Processing bitstream constraints relating to inter-layer prediction types in multi-layer video coding

ABSTRACT

An apparatus for coding video information may include computing hardware configured to: when a current picture is to be predicted using at least inter layer motion prediction (ILMP): process a collocated reference index value associated with the current picture, wherein the collocated reference index value indicates a first reference picture that is used in predicting the current picture using inter layer prediction (ILP); and determine whether the first reference picture indicated by the collocated reference index value is enabled for ILMP; when the current picture is to be predicted using at least inter layer sample prediction (ILSP): process a reference index value associated with a block in the current picture, wherein the reference index value indicates a second reference picture that is used in predicting the block in the current picture using ILP; and determine whether the second reference picture indicated by the reference index value is enabled for ILSP.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/833,836, filed Jun. 11, 2013, and U.S. Provisional Application No.61/859,702, filed Jul. 29, 2013, each of which is incorporated byreference in its entirety.

BACKGROUND

1. Field

This disclosure is related to the field of video coding and compression.In particular, it is related to scalable video coding (SVC), includingSVC for Advanced Video Coding (AVC), as well as SVC for High EfficiencyVideo Coding (HEVC), which is also referred to as Scalable HEVC (SHVC).It is also related to 3D video coding, such as the multiview extensionof HEVC, referred to as MV-HEVC. Various embodiments relate to systemsand methods for independent control of inter-layer motion predictionreference resampling and inter-layer sample prediction referenceresampling and for processing bitstream constraints relating tointer-layer prediction types.

2. Description of the Related Art

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, tablet computers, e-book readers, digitalcameras, digital recording devices, digital media players, video gamingdevices, video game consoles, cellular or satellite radio telephones,so-called “smart phones,” video teleconferencing devices, videostreaming devices, and the like. Digital video devices implement videocoding techniques, such as those described in the standards defined byMPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced VideoCoding (AVC), the High Efficiency Video Coding (HEVC) standard presentlyunder development, and extensions of such standards. The video devicesmay transmit, receive, encode, decode, and/or store digital videoinformation more efficiently by implementing such video codingtechniques.

Video coding techniques include spatial (intra-picture) predictionand/or temporal (inter-picture) prediction to reduce or removeredundancy inherent in video sequences. For block-based video coding, avideo slice (e.g., a video frame or a portion of a video frame) may bepartitioned into video blocks, which may also be referred to astreeblocks, coding units (CUs) and/or coding nodes. Video blocks in anintra-coded (I) slice of a picture are encoded using spatial predictionwith respect to reference samples in neighboring blocks in the samepicture. Video blocks in an inter-coded (P or B) slice of a picture mayuse spatial prediction with respect to reference samples in neighboringblocks in the same picture or temporal prediction with respect toreference samples in other reference pictures. Pictures may be referredto as frames, and reference pictures may be referred to a referenceframes.

Spatial or temporal prediction results in a predictive block for a blockto be coded. Residual data represents pixel differences between theoriginal block to be coded and the predictive block. An inter-codedblock is encoded according to a motion vector that points to a block ofreference samples forming the predictive block, and the residual dataindicating the difference between the coded block and the predictiveblock. An intra-coded block is encoded according to an intra-coding modeand the residual data. For further compression, the residual data may betransformed from the pixel domain to a transform domain, resulting inresidual transform coefficients, which then may be quantized. Thequantized transform coefficients, initially arranged in atwo-dimensional array, may be scanned in order to produce aone-dimensional vector of transform coefficients, and entropy coding maybe applied to achieve even more compression.

SUMMARY

In general, this disclosure describes techniques related to scalablevideo coding (SVC). Various techniques described below provide describemethods and devices for independent control of inter-layer motionprediction reference resampling and inter-layer sample predictionreference resampling. Various techniques described below providedescribe methods and devices for processing bitstream constraintsrelating to inter-layer prediction types.

An apparatus for coding video information according to certain aspectsincludes a memory and computing hardware. The memory unit is configuredto store video information. The computing hardware is configured to:identify a current picture to be predicted using at least one type ofinter layer prediction (ILP), the type of ILP comprising one or more ofinter layer motion prediction (ILMP) or inter layer sample prediction(ILSP); and control: (1) a number of pictures that may be resampled andused to predict the current picture using ILMP and (2) a number ofpictures that may be resampled and used to predict the current pictureusing ILSP, wherein the computing hardware is configured to control thenumber of pictures that may be resampled and used to predict the currentpicture using ILMP independent of the number of pictures that may beresampled and used to predict the current picture using ILSP.

An apparatus for coding video information according to certain aspectsincludes a memory and computing hardware. The memory unit is configuredto store video information. The computing hardware is configured to:identify a current picture to be predicted using at least one type ofinter layer prediction (ILP), the type of ILP comprising inter layermotion prediction (ILMP), or inter layer sample prediction (ILSP), orboth; when the current picture is to be predicted using at least ILMP:process a collocated reference index value associated with the currentpicture, wherein the collocated reference index value indicates a firstreference picture that is used in predicting the current picture usingILMP; and determine whether the first reference picture indicated by thecollocated reference index value is enabled for ILMP; and when thecurrent picture is to be predicted using at least ILSP: process areference index value associated with a block in the current picture,wherein the reference index value indicates a second reference picturethat is used in predicting the block in the current picture using ILSP;and determine whether the second reference picture indicated by thereference index value is enabled for ILSP.

The details of one or more examples are set forth in the accompanyingdrawings and the description below, which are not intended to limit thefull scope of the inventive concepts described herein. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the drawings, reference numbers may be re-used to indicatecorrespondence between referenced elements. The drawings are provided toillustrate example embodiments described herein and are not intended tolimit the scope of the disclosure.

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system that may utilize techniques in accordance with aspectsdescribed in this disclosure.

FIG. 2A is a block diagram illustrating an example of a video encoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 2B is a block diagram illustrating an example of a video encoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 3A is a block diagram illustrating an example of a video decoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 3B is a block diagram illustrating an example of a video decoderthat may implement techniques in accordance with aspects described inthis disclosure.

FIG. 4 is a flowchart illustrating an example method for independentcontrol of inter-layer motion prediction reference resampling andinter-layer sample prediction reference resampling, according to aspectsof this disclosure.

FIG. 5 is a flowchart illustrating an example method for processingbitstream constraints relating to inter-layer prediction types.

DETAILED DESCRIPTION

The techniques described in this disclosure generally relate to scalablevideo coding (SHVC, SVC) and multiview/3D video coding (e.g., multiviewcoding plus depth, MVC+D). For example, the techniques may be relatedto, and used with or within, a High Efficiency Video Coding (HEVC)scalable video coding (SVC, sometimes referred to as SHVC) extension. Inan SHVC, SVC extension, there could be multiple layers of videoinformation. The layer at the lowest level of the video information mayserve as a base layer (BL) or reference layer (RL), and the layer at thevery top (or the highest layer) of the video information may serve as anenhanced layer (EL). The “enhanced layer” is sometimes referred to as an“enhancement layer,” and these terms may be used interchangeably. Thebase layer is sometimes referred to as a “reference layer,” and theseterms may also be used interchangeably. All layers in between the baselayer and the top layer may serve as additional ELs and/or referencelayers. For example, a given layer may be an EL for a layer below (e.g.,that precedes) the given layer, such as the base layer or anyintervening enhancement layer. Further, the given layer may also serveas a RL for one or more the enhancement layer(s) above (e.g., subsequentto) the given layer. Any layer in between the base layer (e.g., thelowest layer having, for example, a layer identification (ID) set orequal to “1”) and the top layer (or the highest layer) may be used as areference for inter-layer prediction by a layer higher to the givenlayer and may use a layer lower to the given layer as a reference forinter-layer prediction. For example, the given layer can be determinedusing a layer lower to the given layer as a reference for inter-layerprediction.

For simplicity, examples are presented in terms of just two layers: a BLand an EL; however, it should be well understood that the ideas andembodiments described below are applicable to cases with multiplelayers, as well. In addition, for ease of explanation, the terms“frames” or “blocks” are often used. However, these terms are not meantto be limiting. For example, the techniques described below can be usedwith any of a variety of video units, including but not limited topixels, blocks (e.g., CU, PU, TU, macroblocks, etc.), slices, frames,picture, etc.

Video Coding

Video coding standards include ITU-T H.261, ISO/IEC MPEG-1 Visual, ITU-TH.262 or ISO/IEC MPEG-2 Visual, ITU-T H.263, ISO/IEC MPEG-4 Visual andITU-T H.264 (also known as ISO/IEC MPEG-4 AVC), including its ScalableVideo Coding (SVC) and Multi-view Video Coding (MVC) and Multi-viewCoding plus Depth (MVC+D) extensions. The latest HEVC draftspecification, and referred to as HEVC WD10 hereinafter, is availablefromhttp://phenix.int-evry.fr/jct/doc_end_user/documents/12_Geneva/wg11/JCTVC-L1003-v34.zip.The multiview extension to HEVC, namely MV-HEVC, is also being developedby the JCT-3V. A recent Working Draft (WD) of MV-HEVC WD3 hereinafter,is available fromhttp://phenix.it-sudparis.eu/jct2/doc_end_user/documents/3_Geneva/wg11/JCT3V-C1004-v4.zip.The scalable extension to HEVC, named SHVC, is also being developed bythe JCT-VC. A recent Working Draft (WD) of SHVC and referred to as SHVCWD2 hereinafter, is available fromhttp://phenix.int-evry.fr/jct/doc_end_user/documents/13_Incheon/wg11/JCTVC-M1008-v1.zip.

In SVC and SHVC, video information may be provided as multiple layers.The layer at the very bottom level can just serve as a base layer (BL)and the layer at the very top level can serve as an enhancement layer(EL). All the layers between the top and bottom layers may serve as bothenhancement layers and reference layers. For example, a layer in themiddle can be an EL for the layers below it, and at the same time as aRL for the layers above it. For simplicity of description, we can assumethat there are two layers, a BL and an EL, in illustrating thetechniques described below. However, all the techniques described hereinare applicable to cases with multiple (more than two) layers, as well.

Scalable video coding (SVC) may be used to provide quality (alsoreferred to as signal-to-noise (SNR)) scalability, spatial scalabilityand/or temporal scalability. For example, in one embodiment, a referencelayer (e.g., a base layer) includes video information sufficient todisplay a video at a first quality level and the enhancement layerincludes additional video information relative to the reference layersuch that the reference layer and the enhancement layer together includevideo information sufficient to display the video at a second qualitylevel higher than the first level (e.g., less noise, greater resolution,better frame rate, etc.). An enhanced layer may have different spatialresolution than a base layer. For example, the spatial aspect ratiobetween EL and BL can be 1.0, 1.5, 2.0 or other different ratios. Inother words, the spatial aspect of the EL may equal 1.0, 1.5, or 2.0times the spatial aspect of the BL. In some examples, the scaling factorof the EL may be greater than the BL. For example, a size of pictures inthe EL may be greater than a size of pictures in the BL. In this way, itmay be possible, although not a limitation, that the spatial resolutionof the EL is larger than the spatial resolution of the BL.

In SVC, which refers to the SVC extension for H.264 or the SHVCextension for H.265 (as discussed above), prediction of a current blockmay be performed using the different layers that are provided for SVC.Such prediction may be referred to as inter-layer prediction.Inter-layer prediction methods may be utilized in SVC in order to reduceinter-layer redundancy. Some examples of inter-layer prediction mayinclude inter-layer intra prediction, inter-layer motion prediction, andinter-layer residual prediction. Inter-layer intra prediction uses thereconstruction of co-located blocks in the base layer to predict thecurrent block in the enhancement layer. Inter-layer motion predictionuses motion information (including motion vectors) of the base layer topredict motion in the enhancement layer. Inter-layer residual predictionuses the residue of the base layer to predict the residue of theenhancement layer.

OVERVIEW

In SHVC, an inter-layer reference picture (ILRP) used in inter-layerprediction (ILP) may be used for inter-layer motion prediction (ILMP),inter-layer sample prediction (ILSP), or both. The type of ILP an ILRPis used for can be referred to as inter-layer prediction type (e.g.,ILMP, ILSP, or both). For a reference picture used for ILSP only, if thereference layer picture has a different picture size from the currentpicture, the reference layer picture should be sample-resampled togenerate the ILRP, but not motion-resampled since motion information isnot used. For a reference picture used for ILMP only, if the referencelayer picture has a different picture size from the current picture, thereference layer picture should be motion-resampled to generate ILRP, butnot sample-resampled since samples from the reference layer picture arenot used. For a reference picture used for both ILSP and ILMP, if thereference picture has a different size from the current picture, thereference layer picture should be sample-resampled and motion-resampled.

In the early versions of SHVC Working Draft (WD), if a reference layerpicture has a different size from the current picture, the resamplingprocess is invoked to derive the inter-layer reference picture withoutchecking the inter-layer prediction type (e.g., ILMP, ILSP, or both) ofthe reference layer picture. This can lead to sample-resampling an ILRPused only for ILMP even though the samples from the ILRP are not needed.Moreover, in some SHVC profiles, the number of inter-layer referencepictures that can be resampled for decoding any particular picture canbe limited to a certain number (e.g., 1). However, the two resamplingprocesses (e.g., sample-resampling and motion-resampling) were notseparately considered in counting the number of resampled pictures.Accordingly, if the sample-resampling process is invoked for a pictureused for inter-layer motion prediction only, then the sample-resamplingprocess can no longer be invoked for another picture for inter-layersample prediction when decoding the particular picture. Therefore, itwould be advantageous to not sample-resample an ILRP used only for ILMP,and also to not count the sample-resampling of an ILRP used only forILMP toward the limit on number of ILRP resampled for a particularpicture. In another example, if the motion-resampling process is invokedfor a picture used for ILSP only, then the motion-resampling process canno longer be invoked for another picture for ILMP when decoding theparticular picture. It would also be advantageous to not motion-resamplean ILRP used only for ILSP, and also to not count the motion-resamplingof an ILRP used only for ILSP toward the limit on number of ILRPresampled for a particular picture. To facilitate discussion, the limiton number of ILRP resampled for a particular picture may also bereferred to as “resampled picture count.”

In order to address these and other challenges, the techniques can avoidinvoking the resampling process for inter-layer reference pictures usedfor inter-layer motion prediction only. The techniques can also notcount inter-layer reference pictures used for only inter-layer motionprediction towards the resampled picture count even when the ILRPs havedifferent picture size from the current picture.

In certain embodiments, the techniques can count inter-layer referencepictures used for inter-layer motion prediction separately from theinter-layer reference pictures used for inter-layer sample predictionwith respect to the constraint on the number of the resampled pictures.For example, the techniques can have one resampled picture count forILRPs for ILMP, and another resampled picture count for ILRPs for ILSP.

In addition, the techniques can also provide and/or process bitstreamconstraints relating to inter-layer prediction types. For example, thetechniques can provide and/or process a bitstream constraint that thecollocated reference index (e.g., collocated_ref_idx) can only refer toan ILRP used for at least ILMP. The techniques can also provide and/orprocess a bitstream constraint that reference index (e.g., ref_idx) canonly refer to an ILRP used for at least ILSP. The bitstream constraintscan be implemented using one or more flags.

Various aspects of the novel systems, apparatuses, and methods aredescribed more fully hereinafter with reference to the accompanyingdrawings. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to any specific structureor function presented throughout this disclosure. Rather, these aspectsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the disclosure to those skilled in theart. Based on the teachings herein one skilled in the art shouldappreciate that the scope of the disclosure is intended to cover anyaspect of the novel systems, apparatuses, and methods disclosed herein,whether implemented independently of, or combined with, any other aspectof the invention. For example, an apparatus may be implemented or amethod may be practiced using any number of the aspects set forthherein. In addition, the scope of the invention is intended to coversuch an apparatus or method which is practiced using other structure,functionality, or structure and functionality in addition to or otherthan the various aspects of the invention set forth herein. It should beunderstood that any aspect disclosed herein may be embodied by one ormore elements of a claim.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

Video Coding System

FIG. 1 is a block diagram that illustrates an example video codingsystem 10 that may utilize techniques in accordance with aspectsdescribed in this disclosure. As used described herein, the term “videocoder” refers generically to both video encoders and video decoders. Inthis disclosure, the terms “video coding” or “coding” may refergenerically to video encoding and video decoding.

As shown in FIG. 1, video coding system 10 includes a source device 12and a destination device 14. Source device 12 generates encoded videodata. Destination device 14 may decode the encoded video data generatedby source device 12. Source device 12 can provide the video data to thedestination device 14 via a communication channel 16, which may includea computer-readable storage medium or other communication channel.Source device 12 and destination device 14 may include a wide range ofdevices, including desktop computers, notebook (e.g., laptop) computers,tablet computers, set-top boxes, telephone handsets, such as so-called“smart” phones, so-called “smart” pads, televisions, cameras, displaydevices, digital media players, video gaming consoles, in-car computers,video streaming devices, or the like. Source device 12 and destinationdevice 14 may be equipped for wireless communication.

Destination device 14 may receive the encoded video data to be decodedvia communication channel 16. Communication channel 16 may comprise atype of medium or device capable of moving the encoded video data fromsource device 12 to destination device 14. For example, communicationchannel 16 may comprise a communication medium to enable source device12 to transmit encoded video data directly to destination device 14 inreal-time. The encoded video data may be modulated according to acommunication standard, such as a wireless communication protocol, andtransmitted to destination device 14. The communication medium maycomprise a wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network, such asthe Internet. The communication medium may include routers, switches,base stations, or other equipment that may be useful to facilitatecommunication from source device 12 to destination device 14.

In some embodiments, encoded data may be output from output interface 22to a storage device. In such examples, channel 16 may correspond to astorage device or computer-readable storage medium that stores theencoded video data generated by source device 12. For example,destination device 14 may access the computer-readable storage mediumvia disk access or card access. Similarly, encoded data may be accessedfrom the computer-readable storage medium by input interface 28. Thecomputer-readable storage medium may include any of a variety ofdistributed or locally accessed data storage media such as a hard drive,Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile or non-volatilememory, or other digital storage media for storing video data. Thecomputer-readable storage medium may correspond to a file server oranother intermediate storage device that may store the encoded videogenerated by source device 12. Destination device 14 may access storedvideo data from the computer-readable storage medium via streaming ordownload. The file server may be a type of server capable of storingencoded video data and transmitting that encoded video data to thedestination device 14. Example file servers include a web server (e.g.,for a website), an FTP server, network attached storage (NAS) devices,or a local disk drive. Destination device 14 may access the encodedvideo data through a standard data connection, including an Internetconnection. This may include a wireless channel (e.g., a Wi-Ficonnection), a wired connection (e.g., DSL, cable modem, etc.), or acombination of both that is suitable for accessing encoded video datastored on a file server. The transmission of encoded video data from thecomputer-readable storage medium may be a streaming transmission, adownload transmission, or a combination of both.

The techniques of this disclosure can apply applications or settings inaddition to wireless applications or settings. The techniques may beapplied to video coding in support of a of a variety of multimediaapplications, such as over-the-air television broadcasts, cabletelevision transmissions, satellite television transmissions, Internetstreaming video transmissions, such as dynamic adaptive streaming overHTTP (DASH), digital video that is encoded onto a data storage medium,decoding of digital video stored on a data storage medium, or otherapplications. In some embodiments, system 10 may be configured tosupport one-way or two-way video transmission to support applicationssuch as video streaming, video playback, video broadcasting, and/orvideo telephony.

In FIG. 1, source device 12 includes video source 18, video encoder 20,and output interface 22. Destination device 14 includes input interface28, video decoder 30, and display device 32. Video encoder 20 of sourcedevice 12 may be configured to apply the techniques for coding abitstream including video data conforming to multiple standards orstandard extensions. In other embodiments, a source device and adestination device may include other components or arrangements. Forexample, source device 12 may receive video data from an external videosource 18, such as an external camera. Likewise, destination device 14may interface with an external display device, rather than including anintegrated display device.

Video source 18 of source device 12 may include a video capture device,such as a video camera, a video archive containing previously capturedvideo, and/or a video feed interface to receive video from a videocontent provider. Video source 18 may generate computer graphics-baseddata as the source video, or a combination of live video, archivedvideo, and computer-generated video. In some embodiments, if videosource 18 is a video camera, source device 12 and destination device 14may form so-called camera phones or video phones. The captured,pre-captured, or computer-generated video may be encoded by videoencoder 20. The encoded video information may be output by outputinterface 22 to a communication channel 16, which may include acomputer-readable storage medium, as discussed above.

Computer-readable storage medium may include transient media, such as awireless broadcast or wired network transmission, or storage media(e.g., non-transitory storage media), such as a hard disk, flash drive,compact disc, digital video disc, Blu-ray disc, or othercomputer-readable media. A network server (not shown) may receiveencoded video data from source device 12 and provide the encoded videodata to destination device 14 (e.g., via network transmission). Acomputing device of a medium production facility, such as a discstamping facility, may receive encoded video data from source device 12and produce a disc containing the encoded video data. Therefore,communication channel 16 may be understood to include one or morecomputer-readable storage media of various forms.

Input interface 28 of destination device 14 can receive information fromcommunication channel 16. The information of communication channel 16may include syntax information defined by video encoder 20, which can beused by video decoder 30, that includes syntax elements that describecharacteristics and/or processing of blocks and other coded units, e.g.,GOPs. Display device 32 displays the decoded video data to a user, andmay include any of a variety of display devices such as a cathode raytube (CRT), a liquid crystal display (LCD), a plasma display, an organiclight emitting diode (OLED) display, or another type of display device.

Video encoder 20 and video decoder 30 may operate according to a videocoding standard, such as the High Efficiency Video Coding (HEVC)standard presently under development, and may conform to the HEVC TestModel (HM). Alternatively, video encoder 20 and video decoder 30 mayoperate according to other proprietary or industry standards, such asthe ITU-T H.264 standard, alternatively referred to as MPEG-4, Part 10,Advanced Video Coding (AVC), or extensions of such standards. Thetechniques of this disclosure, however, are not limited to anyparticular coding standard. Other examples of video coding standardsinclude MPEG-2 and ITU-T H.263. Although not shown in FIG. 1, in someaspects, video encoder 20 and video decoder 30 may each be integratedwith an audio encoder and decoder, and may include appropriate MUX-DEMUXunits, or other hardware and software, to handle encoding of both audioand video in a common data stream or separate data streams. Ifapplicable, MUX-DEMUX units may conform to the ITU H.223 multiplexerprotocol, or other protocols such as the user datagram protocol (UDP).

FIG. 1 is merely an example and the techniques of this disclosure mayapply to video coding settings (e.g., video encoding or video decoding)that do not necessarily include any data communication between theencoding and decoding devices. In other examples, data can be retrievedfrom a local memory, streamed over a network, or the like. An encodingdevice may encode and store data to memory, and/or a decoding device mayretrieve and decode data from memory. In many examples, the encoding anddecoding is performed by devices that do not communicate with oneanother, but simply encode data to memory and/or retrieve and decodedata from memory.

Video encoder 20 and video decoder 30 each may be implemented as any ofa variety of suitable encoder circuitry, such as one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs),discrete logic, software, hardware, firmware or any combinationsthereof. When the techniques are implemented partially in software, adevice may store instructions for the software in a non-transitorycomputer-readable medium and execute the instructions in hardware usingone or more processors to perform the techniques of this disclosure.Each of video encoder 20 and video decoder 30 may be included in one ormore encoders or decoders, either of which may be integrated as part ofa combined encoder/decoder (CODEC) in a respective device. A deviceincluding video encoder 20 and/or video decoder 30 may comprise anintegrated circuit, a microprocessor, and/or a wireless communicationdevice, such as a cellular telephone.

The JCT-VC is working on development of the HEVC standard and itsextension and Version 1 has been finalized. The HEVC standardizationefforts are based on an evolving model of a video coding device referredto as the HEVC Test Model (HM). The HM presumes several additionalcapabilities of video coding devices relative to existing devicesaccording to, e.g., ITU-T H.264/AVC. For example, whereas H.264 providesnine intra-prediction encoding modes, the HM may provide as many asthirty-three intra-prediction encoding modes.

In general, the working model of the HM describes that a video frame orpicture may be divided into a sequence of treeblocks or largest codingunits (LCU) that include both luma and chroma samples. Syntax datawithin a bitstream may define a size for the LCU, which is a largestcoding unit in terms of the number of pixels. A slice includes a numberof consecutive treeblocks in coding order. A video frame or picture maybe partitioned into one or more slices. Each treeblock may be split intocoding units (CUs) according to a quadtree. In general, a quadtree datastructure includes one node per CU, with a root node corresponding tothe treeblock. If a CU is split into four sub-CUs, the nodecorresponding to the CU includes four leaf nodes, each of whichcorresponds to one of the sub-CUs.

Each node of the quadtree data structure may provide syntax data for thecorresponding CU. For example, a node in the quadtree may include asplit flag, indicating whether the CU corresponding to the node is splitinto sub-CUs. Syntax elements for a CU may be defined recursively, andmay depend on whether the CU is split into sub-CUs. If a CU is not splitfurther, it is referred as a leaf-CU. In this disclosure, four sub-CUsof a leaf-CU will also be referred to as leaf-CUs even if there is noexplicit splitting of the original leaf-CU. For example, if a CU at16×16 size is not split further, the four 8×8 sub-CUs will also bereferred to as leaf-CUs although the 16×16 CU was never split.

A CU has a similar purpose as a macroblock of the H.264 standard, exceptthat a CU does not have a size distinction. For example, a treeblock maybe split into four child nodes (also referred to as sub-CUs), and eachchild node may in turn be a parent node and be split into another fourchild nodes. A final, unsplit child node, referred to as a leaf node ofthe quadtree, comprises a coding node, also referred to as a leaf-CU.Syntax data associated with a coded bitstream may define a maximumnumber of times a treeblock may be split, referred to as a maximum CUdepth, and may also define a minimum size of the coding nodes.Accordingly, a bitstream may also define a smallest coding unit (SCU).This disclosure uses the term “block” to refer to any of a CU, PU, orTU, in the context of HEVC, or similar data structures in the context ofother standards (e.g., macroblocks and sub-blocks thereof in H.264/AVC).

A CU includes a coding node and prediction units (PUs) and transformunits (TUs) associated with the coding node. A size of the CUcorresponds to a size of the coding node and must be square in shape.The size of the CU may range from 8×8 pixels up to the size of thetreeblock with a maximum of 64×64 pixels or greater. Each CU may containone or more PUs and one or more TUs. Syntax data associated with a CUmay describe, for example, partitioning of the CU into one or more PUs.Partitioning modes may differ between whether the CU is skip or directmode encoded, intra-prediction mode encoded, or inter-prediction modeencoded. PUs may be partitioned to be non-square in shape. Syntax dataassociated with a CU may also describe, for example, partitioning of theCU into one or more TUs according to a quadtree. A TU can be square ornon-square (e.g., rectangular) in shape.

The HEVC standard allows for transformations according to TUs, which maybe different for different CUs. The TUs are typically sized based on thesize of PUs within a given CU defined for a partitioned LCU, althoughthis may not always be the case. The TUs are typically the same size orsmaller than the PUs. In some examples, residual samples correspondingto a CU may be subdivided into smaller units using a quadtree structureknown as “residual quad tree” (RQT). The leaf nodes of the RQT may bereferred to as transform units (TUs). Pixel difference values associatedwith the TUs may be transformed to produce transform coefficients, whichmay be quantized.

A leaf-CU may include one or more prediction units (PUs). In general, aPU represents a spatial area corresponding to all or a portion of thecorresponding CU, and may include data for retrieving a reference samplefor the PU. Moreover, a PU includes data related to prediction. Forexample, when the PU is intra-mode encoded, data for the PU may beincluded in a residual quadtree (RQT), which may include data describingan intra-prediction mode for a TU corresponding to the PU. As anotherexample, when the PU is inter-mode encoded, the PU may include datadefining one or more motion vectors for the PU. The data defining themotion vector for a PU may describe, for example, a horizontal componentof the motion vector, a vertical component of the motion vector, aresolution for the motion vector (e.g., one-quarter pixel precision orone-eighth pixel precision), a reference picture to which the motionvector points, and/or a reference picture list (e.g., List 0, List 1, orList C) for the motion vector.

A leaf-CU having one or more PUs may also include one or more transformunits (TUs). The transform units may be specified using an RQT (alsoreferred to as a TU quadtree structure), as discussed above. Forexample, a split flag may indicate whether a leaf-CU is split into fourtransform units. Then, each transform unit may be split further intofurther sub-TUs. When a TU is not split further, it may be referred toas a leaf-TU. Generally, for intra coding, all the leaf-TUs belonging toa leaf-CU share the same intra prediction mode. That is, the sameintra-prediction mode is generally applied to calculate predicted valuesfor all TUs of a leaf-CU. For intra coding, a video encoder maycalculate a residual value for each leaf-TU using the intra predictionmode, as a difference between the portion of the CU corresponding to theTU and the original block. A TU is not necessarily limited to the sizeof a PU. Thus, TUs may be larger or smaller than a PU. For intra coding,a PU may be collocated with a corresponding leaf-TU for the same CU. Insome examples, the maximum size of a leaf-TU may correspond to the sizeof the corresponding leaf-CU.

Moreover, TUs of leaf-CUs may also be associated with respectivequadtree data structures, referred to as residual quadtrees (RQTs). Thatis, a leaf-CU may include a quadtree indicating how the leaf-CU ispartitioned into TUs. The root node of a TU quadtree generallycorresponds to a leaf-CU, while the root node of a CU quadtree generallycorresponds to a treeblock (or LCU). TUs of the RQT that are not splitare referred to as leaf-TUs. In general, this disclosure uses the termsCU and TU to refer to leaf-CU and leaf-TU, respectively, unless notedotherwise.

A video sequence typically includes a series of video frames orpictures. A group of pictures (GOP) generally comprises a series of oneor more of the video pictures. A GOP may include syntax data in a headerof the GOP, a header of one or more of the pictures, or elsewhere, thatdescribes a number of pictures included in the GOP. Each slice of apicture may include slice syntax data that describes an encoding modefor the respective slice. Video encoder 20 typically operates on videoblocks within individual video slices in order to encode the video data.A video block may correspond to a coding node within a CU. The videoblocks may have fixed or varying sizes, and may differ in size accordingto a specified coding standard.

As an example, the HM supports prediction in various PU sizes. Assumingthat the size of a particular CU is 2N×2N, the HM supportsintra-prediction in PU sizes of 2N×2N or N×N, and inter-prediction insymmetric PU sizes of 2N×2N, 2N×N, N×2N, or N×N. The HM also supportsasymmetric partitioning for inter-prediction in PU sizes of 2N×nU,2N×nD, nL×2N, and nR×2N. In asymmetric partitioning, one direction of aCU is not partitioned, while the other direction is partitioned into 25%and 75%. The portion of the CU corresponding to the 25% partition isindicated by an “n” followed by an indication of “Up”, “Down,” “Left,”or “Right.” Thus, for example, “2N×nU” refers to a 2N×2N CU that ispartitioned horizontally with a 2N×0.5N PU on top and a 2N×1.5N PU onbottom.

In this disclosure, “N×N” and “N by N” may be used interchangeably torefer to the pixel dimensions of a video block in terms of vertical andhorizontal dimensions, e.g., 16×16 pixels or 16 by 16 pixels. Ingeneral, a 16×16 block will have 16 pixels in a vertical direction(y=16) and 16 pixels in a horizontal direction (x=16). Likewise, an N×Nblock generally has N pixels in a vertical direction and N pixels in ahorizontal direction, where N represents a nonnegative integer value.The pixels in a block may be arranged in rows and columns. Moreover,blocks need not necessarily have the same number of pixels in thehorizontal direction as in the vertical direction. For example, blocksmay comprise N×M pixels, where M is not necessarily equal to N.

Following intra-predictive or inter-predictive coding using the PUs of aCU, video encoder 20 may calculate residual data for the TUs of the CU.The PUs may comprise syntax data describing a method or mode ofgenerating predictive pixel data in the spatial domain (also referred toas the pixel domain) and the TUs may comprise coefficients in thetransform domain following application of a transform, e.g., a discretesine transform (DST), a discrete cosine transform (DCT), an integertransform, a wavelet transform, or a conceptually similar transform toresidual video data. The residual data may correspond to pixeldifferences between pixels of the unencoded picture and predictionvalues corresponding to the PUs. Video encoder 20 may form the TUsincluding the residual data for the CU, and then transform the TUs toproduce transform coefficients for the CU.

Following any transforms to produce transform coefficients, videoencoder 20 may perform quantization of the transform coefficients.Quantization is a broad term intended to have its broadest ordinarymeaning. In one embodiment, quantization refers to a process in whichtransform coefficients are quantized to possibly reduce the amount ofdata used to represent the coefficients, providing further compression.The quantization process may reduce the bit depth associated with someor all of the coefficients. For example, an n-bit value may be roundeddown to an m-bit value during quantization, where n is greater than m.

Following quantization, the video encoder may scan the transformcoefficients, producing a one-dimensional vector from thetwo-dimensional matrix including the quantized transform coefficients.The scan may be designed to place higher energy (and therefore lowerfrequency) coefficients at the front of the array and to place lowerenergy (and therefore higher frequency) coefficients at the back of thearray. In some examples, video encoder 20 may utilize a predefined scanorder to scan the quantized transform coefficients to produce aserialized vector that can be entropy encoded. In other examples, videoencoder 20 may perform an adaptive scan. After scanning the quantizedtransform coefficients to form a one-dimensional vector, video encoder20 may entropy encode the one-dimensional vector, e.g., according tocontext-adaptive variable length coding (CAVLC), context-adaptive binaryarithmetic coding (CABAC), syntax-based context-adaptive binaryarithmetic coding (SBAC), Probability Interval Partitioning Entropy(PIPE) coding or another entropy encoding methodology. Video encoder 20may also entropy encode syntax elements associated with the encodedvideo data for use by video decoder 30 in decoding the video data.

To perform CABAC, video encoder 20 may assign a context within a contextmodel to a symbol to be transmitted. The context may relate to, forexample, whether neighboring values of the symbol are non-zero or not.To perform CAVLC, video encoder 20 may select a variable length code fora symbol to be transmitted. Codewords in VLC may be constructed suchthat relatively shorter codes correspond to more probable symbols, whilelonger codes correspond to less probable symbols. In this way, the useof VLC may achieve a bit savings over, for example, using equal-lengthcodewords for each symbol to be transmitted. The probabilitydetermination may be based on a context assigned to the symbol.

Video encoder 20 may further send syntax data, such as block-basedsyntax data, frame-based syntax data, and GOP-based syntax data, tovideo decoder 30, e.g., in a frame header, a block header, a sliceheader, or a GOP header. The GOP syntax data may describe a number offrames in the respective GOP, and the frame syntax data may indicate anencoding/prediction mode used to encode the corresponding frame.

Video Encoder

FIG. 2A is a block diagram illustrating an example of a video encoderthat may implement techniques in accordance with aspects described inthis disclosure. Video encoder 20 may be configured to process a singlelayer of a video bitstream, such as for HEVC. Further, video encoder 20may be configured to perform any or all of the techniques of thisdisclosure, including but not limited to the methods of independentcontrol of inter-layer motion prediction reference resampling andinter-layer sample prediction reference resampling, methods ofprocessing bitstream constraints relating to inter-layer predictiontypes, and related processes described in greater detail above and belowwith respect to FIGS. 4-5. As one example, inter-layer prediction unit66 (when provided) may be configured to perform any or all of thetechniques described in this disclosure. However, aspects of thisdisclosure are not so limited. In some examples, the techniquesdescribed in this disclosure may be shared among the various componentsof video encoder 20. In some examples, additionally or alternatively, aprocessor (not shown) may be configured to perform any or all of thetechniques described in this disclosure.

For purposes of explanation, this disclosure describes video encoder 20in the context of HEVC coding. However, the techniques of thisdisclosure may be applicable to other coding standards or methods. Theencoder 20 of FIG. 2A illustrates a single layer of a codec. However, aswill be described further with respect to FIG. 2B, some or all of thevideo encoder 20 may be duplicated for processing according to amulti-layer codec.

Video encoder 20 may perform intra-, inter-, and inter-layer prediction(sometime referred to as intra-, inter- or inter-layer coding) of videoblocks within video slices. Intra coding relies on spatial prediction toreduce or remove spatial redundancy in video within a given video frameor picture. Inter-coding relies on temporal prediction to reduce orremove temporal redundancy in video within adjacent frames or picturesof a video sequence. Inter-layer coding relies on prediction based uponvideo within a different layer(s) within the same video coding sequence.Intra-mode (I mode) may refer to any of several spatial based codingmodes. Inter-modes, such as uni-directional prediction (P mode) orbi-prediction (B mode), may refer to any of several temporal-basedcoding modes.

As shown in FIG. 2A, video encoder 20 receives a current video blockwithin a video frame to be encoded. In the example of FIG. 2A, videoencoder 20 includes mode select unit 40, reference frame memory 64,summer 50, transform processing unit 52, quantization unit 54, andentropy encoding unit 56. Mode select unit 40, in turn, includes motioncompensation unit 44, motion estimation unit 42, intra-prediction unit46, inter-layer prediction unit 66, and partition unit 48. Referenceframe memory 64 may include a decoded picture buffer. The decodedpicture buffer is a broad term having its ordinary meaning, and in someembodiments refers to a video codec-managed data structure of referenceframes.

For video block reconstruction, video encoder 20 also includes inversequantization unit 58, inverse transform unit 60, and summer 62. Adeblocking filter (not shown in FIG. 2A) may also be included to filterblock boundaries to remove blockiness artifacts from reconstructedvideo. If desired, the deblocking filter would typically filter theoutput of summer 62. Additional filters (in loop or post loop) may alsobe used in addition to the deblocking filter. Such filters are not shownfor brevity, but if desired, may filter the output of summer 50 (as anin-loop filter).

During the encoding process, video encoder 20 receives a video frame orslice to be coded. The frame or slice may be divided into multiple videoblocks. Motion estimation unit 42 and motion compensation unit 44perform inter-predictive coding of the received video block relative toone or more blocks in one or more reference frames to provide temporalprediction. Intra-prediction unit 46 may alternatively performintra-predictive coding of the received video block relative to one ormore neighboring blocks in the same frame or slice as the block to becoded to provide spatial prediction. Video encoder 20 may performmultiple coding passes, e.g., to select an appropriate coding mode foreach block of video data.

Moreover, partition unit 48 may partition blocks of video data intosub-blocks, based on evaluation of previous partitioning schemes inprevious coding passes. For example, partition unit 48 may initiallypartition a frame or slice into LCUs, and partition each of the LCUsinto sub-CUs based on rate-distortion analysis (e.g., rate-distortionoptimization, etc.). Mode select unit 40 may further produce a quadtreedata structure indicative of partitioning of an LCU into sub-CUs.Leaf-node CUs of the quadtree may include one or more PUs and one ormore TUs.

Mode select unit 40 may select one of the coding modes, intra, inter, orinter-layer prediction mode, e.g., based on error results, and providethe resulting intra-, inter-, or inter-layer coded block to summer 50 togenerate residual block data and to summer 62 to reconstruct the encodedblock for use as a reference frame. Mode select unit 40 also providessyntax elements, such as motion vectors, intra-mode indicators,partition information, and other such syntax information, to entropyencoding unit 56.

Motion estimation unit 42 and motion compensation unit 44 may be highlyintegrated, but are illustrated separately for conceptual purposes.Motion estimation, performed by motion estimation unit 42, is theprocess of generating motion vectors, which estimate motion for videoblocks. A motion vector, for example, may indicate the displacement of aPU of a video block within a current video frame or picture relative toa predictive block within a reference frame (or other coded unit)relative to the current block being coded within the current frame (orother coded unit). A predictive block is a block that is found toclosely match the block to be coded, in terms of pixel difference, whichmay be determined by sum of absolute difference (SAD), sum of squaredifference (SSD), or other difference metrics. In some examples, videoencoder 20 may calculate values for sub-integer pixel positions ofreference pictures stored in reference frame memory 64. For example,video encoder 20 may interpolate values of one-quarter pixel positions,one-eighth pixel positions, or other fractional pixel positions of thereference picture. Therefore, motion estimation unit 42 may perform amotion search relative to the full pixel positions and fractional pixelpositions and output a motion vector with fractional pixel precision.

Motion estimation unit 42 calculates a motion vector for a PU of a videoblock in an inter-coded slice by comparing the position of the PU to theposition of a predictive block of a reference picture. The referencepicture may be selected from a first reference picture list (List 0) ora second reference picture list (List 1), each of which identify one ormore reference pictures stored in reference frame memory 64. Motionestimation unit 42 sends the calculated motion vector to entropyencoding unit 56 and motion compensation unit 44.

Motion compensation, performed by motion compensation unit 44, mayinvolve fetching or generating the predictive block based on the motionvector determined by motion estimation unit 42. Motion estimation unit42 and motion compensation unit 44 may be functionally integrated, insome examples. Upon receiving the motion vector for the PU of thecurrent video block, motion compensation unit 44 may locate thepredictive block to which the motion vector points in one of thereference picture lists. Summer 50 forms a residual video block bysubtracting pixel values of the predictive block from the pixel valuesof the current video block being coded, forming pixel difference values,as discussed below. In some embodiments, motion estimation unit 42 canperform motion estimation relative to luma components, and motioncompensation unit 44 can use motion vectors calculated based on the lumacomponents for both chroma components and luma components. Mode selectunit 40 may generate syntax elements associated with the video blocksand the video slice for use by video decoder 30 in decoding the videoblocks of the video slice.

Intra-prediction unit 46 may intra-predict or calculate a current block,as an alternative to the inter-prediction performed by motion estimationunit 42 and motion compensation unit 44, as described above. Inparticular, intra-prediction unit 46 may determine an intra-predictionmode to use to encode a current block. In some examples,intra-prediction unit 46 may encode a current block using variousintra-prediction modes, e.g., during separate encoding passes, andintra-prediction unit 46 (or mode select unit 40, in some examples) mayselect an appropriate intra-prediction mode to use from the testedmodes.

For example, intra-prediction unit 46 may calculate rate-distortionvalues using a rate-distortion analysis for the various testedintra-prediction modes, and select the intra-prediction mode having thebest rate-distortion characteristics among the tested modes.Rate-distortion analysis generally determines an amount of distortion(or error) between an encoded block and an original, unencoded blockthat was encoded to produce the encoded block, as well as a bitrate(that is, a number of bits) used to produce the encoded block.Intra-prediction unit 46 may calculate ratios from the distortions andrates for the various encoded blocks to determine which intra-predictionmode exhibits the best rate-distortion value for the block.

After selecting an intra-prediction mode for a block, intra-predictionunit 46 may provide information indicative of the selectedintra-prediction mode for the block to entropy encoding unit 56. Entropyencoding unit 56 may encode the information indicating the selectedintra-prediction mode. Video encoder 20 may include in the transmittedbitstream configuration data, which may include a plurality ofintra-prediction mode index tables and a plurality of modifiedintra-prediction mode index tables (also referred to as codeword mappingtables), definitions of encoding contexts for various blocks, andindications of a most probable intra-prediction mode, anintra-prediction mode index table, and a modified intra-prediction modeindex table to use for each of the contexts.

The video encoder 20 may include an inter-layer prediction unit 66.Inter-layer prediction unit 66 is configured to predict a current block(e.g., a current block in the EL) using one or more different layersthat are available in SVC (e.g., a base or reference layer). Suchprediction may be referred to as inter-layer prediction. Inter-layerprediction unit 66 utilizes prediction methods to reduce inter-layerredundancy, thereby improving coding efficiency and reducingcomputational resource requirements. Some examples of inter-layerprediction include inter-layer intra prediction, inter-layer motionprediction, and inter-layer residual prediction. Inter-layer intraprediction uses the reconstruction of co-located blocks in the baselayer to predict the current block in the enhancement layer. Inter-layermotion prediction uses motion information of the base layer to predictmotion in the enhancement layer. Inter-layer residual prediction usesthe residue of the base layer to predict the residue of the enhancementlayer. When the base and enhancement layers have different spatialresolutions, spatial motion vector scaling and/or inter-layer positionmapping using a temporal scaling function may be performed by theinter-layer prediction unit 66, as described in greater detail below.

Video encoder 20 forms a residual video block by subtracting theprediction data from mode select unit 40 from the original video blockbeing coded. Summer 50 represents the component or components thatperform this subtraction operation. Transform processing unit 52 appliesa transform, such as a discrete cosine transform (DCT) or a conceptuallysimilar transform, to the residual block, producing a video blockcomprising residual transform coefficient values. Transform processingunit 52 may perform other transforms which are conceptually similar toDCT. For example, discrete sine transforms (DST), wavelet transforms,integer transforms, sub-band transforms or other types of transforms canalso be used.

Transform processing unit 52 can apply the transform to the residualblock, producing a block of residual transform coefficients. Thetransform may convert the residual information from a pixel value domainto a transform domain, such as a frequency domain. Transform processingunit 52 may send the resulting transform coefficients to quantizationunit 54. Quantization unit 54 quantizes the transform coefficients tofurther reduce bit rate. The quantization process may reduce the bitdepth associated with some or all of the coefficients. The degree ofquantization may be modified by adjusting a quantization parameter. Insome examples, quantization unit 54 may then perform a scan of thematrix including the quantized transform coefficients. Alternatively,entropy encoding unit 56 may perform the scan.

Following quantization, entropy encoding unit 56 entropy encodes thequantized transform coefficients. For example, entropy encoding unit 56may perform context adaptive variable length coding (CAVLC), contextadaptive binary arithmetic coding (CABAC), syntax-based context-adaptivebinary arithmetic coding (SBAC), probability interval partitioningentropy (PIPE) coding or another entropy coding technique. In the caseof context-based entropy coding, context may be based on neighboringblocks. Following the entropy coding by entropy encoding unit 56, theencoded bitstream may be transmitted to another device (e.g., videodecoder 30) or archived for later transmission or retrieval.

Inverse quantization unit 58 and inverse transform unit 60 apply inversequantization and inverse transformation, respectively, to reconstructthe residual block in the pixel domain (e.g., for later use as areference block). Motion compensation unit 44 may calculate a referenceblock by adding the residual block to a predictive block of one of theframes of reference frame memory 64. Motion compensation unit 44 mayalso apply one or more interpolation filters to the reconstructedresidual block to calculate sub-integer pixel values for use in motionestimation. Summer 62 adds the reconstructed residual block to themotion compensated prediction block produced by motion compensation unit44 to produce a reconstructed video block for storage in reference framememory 64. The reconstructed video block may be used by motionestimation unit 42 and motion compensation unit 44 as a reference blockto inter-code a block in a subsequent video frame.

Multi-Layer Video Encoder

FIG. 2B is a block diagram illustrating an example of a multi-layervideo encoder 21 that may implement techniques in accordance withaspects described in this disclosure. The video encoder 21 may beconfigured to process multi-layer video frames, such as for SHVC andmultiview coding. Further, the video encoder 21 may be configured toperform any or all of the techniques of this disclosure.

The video encoder 21 includes a video encoder 20A and video encoder 20B,each of which may be configured as the video encoder 20 of FIG. 2A andmay perform the functions described above with respect to the videoencoder 20. Further, as indicated by the reuse of reference numbers, thevideo encoders 20A and 20B may include at least some of the systems andsubsystems as the video encoder 20. Although the video encoder 21 isillustrated as including two video encoders 20A and 20B, the videoencoder 21 is not limited as such and may include any number of videoencoder 20 layers. In some embodiments, the video encoder 21 may includea video encoder 20 for each picture or frame in an access unit. Forexample, an access unit that includes five pictures may be processed orencoded by a video encoder that includes five encoder layers. In someembodiments, the video encoder 21 may include more encoder layers thanframes in an access unit. In some such cases, some of the video encoderlayers may be inactive when processing some access units.

In addition to the video encoders 20A and 20B, the video encoder 21 mayinclude a resampling unit 90. The resampling unit 90 may, in some cases,upsample a base layer of a received video frame to, for example, createan enhancement layer. The resampling unit 90 may upsample particularinformation associated with the received base layer of a frame, but notother information. For example, the resampling unit 90 may upsample thespatial size or number of pixels of the base layer, but the number ofslices or the picture order count may remain constant. In some cases,the resampling unit 90 may not process the received video and/or may beoptional. For example, in some cases, the mode select unit 40 mayperform upsampling. In some embodiments, the resampling unit 90 isconfigured to upsample a layer and reorganize, redefine, modify, oradjust one or more slices to comply with a set of slice boundary rulesand/or raster scan rules. Although primarily described as upsampling abase layer, or a lower layer in an access unit, in some cases, theresampling unit 90 may downsample a layer. For example, if duringstreaming of a video bandwidth is reduced, a frame may be downsampledinstead of upsampled. Resampling unit 90 may be further configured toperform cropping and/or padding operations, as well.

The resampling unit 90 may be configured to receive a picture or frame(or picture information associated with the picture) from the decodedpicture buffer 114 of the lower layer encoder (e.g., the video encoder20A) and to upsample the picture (or the received picture information).This upsampled picture may then be provided to the mode select unit 40of a higher layer encoder (e.g., the video encoder 20B) configured toencode a picture in the same access unit as the lower layer encoder. Insome cases, the higher layer encoder is one layer removed from the lowerlayer encoder. In other cases, there may be one or more higher layerencoders between the layer 0 video encoder and the layer 1 encoder ofFIG. 2B.

In some cases, the resampling unit 90 may be omitted or bypassed. Insuch cases, the picture from the decoded picture buffer 64 of the videoencoder 20A may be provided directly, or at least without being providedto the resampling unit 90, to the mode select unit 40 of the videoencoder 20B. For example, if video data provided to the video encoder20B and the reference picture from the decoded picture buffer 64 of thevideo encoder 20A are of the same size or resolution, the referencepicture may be provided to the video encoder 20B without any resampling.

In some embodiments, the video encoder 21 downsamples video data to beprovided to the lower layer encoder using the downsampling unit 94before provided the video data to the video encoder 20A. Alternatively,the downsampling unit 94 may be a resampling unit 90 capable ofupsampling or downsampling the video data. In yet other embodiments, thedownsampling unit 94 may be omitted.

As illustrated in FIG. 2B, the video encoder 21 may further include amultiplexor 98, or mux. The mux 98 can output a combined bitstream fromthe video encoder 21. The combined bitstream may be created by taking abitstream from each of the video encoders 20A and 20B and alternatingwhich bitstream is output at a given time. While in some cases the bitsfrom the two (or more in the case of more than two video encoder layers)bitstreams may be alternated one bit at a time, in many cases thebitstreams are combined differently. For example, the output bitstreammay be created by alternating the selected bitstream one block at atime. In another example, the output bitstream may be created byoutputting a non-1:1 ratio of blocks from each of the video encoders 20Aand 20B. For instance, two blocks may be output from the video encoder20B for each block output from the video encoder 20A. In someembodiments, the output stream from the mux 98 may be preprogrammed. Inother embodiments, the mux 98 may combine the bitstreams from the videoencoders 20A, 20B based on a control signal received from a systemexternal to the video encoder 21, such as from a processor on the sourcedevice 12. The control signal may be generated based on the resolutionor bitrate of a video from the video source 18, based on a bandwidth ofthe channel 16, based on a subscription associated with a user (e.g., apaid subscription versus a free subscription), or based on any otherfactor for determining a resolution output desired from the videoencoder 21.

Video Decoder

FIG. 3A is a block diagram illustrating an example of a video decoderthat may implement techniques in accordance with aspects described inthis disclosure. The video decoder 30 may be configured to process asingle layer of a video bitstream, such as for HEVC. Further, videodecoder 30 may be configured to perform any or all of the techniques ofthis disclosure, including but not limited to the methods of independentcontrol of inter-layer motion prediction reference resampling andinter-layer sample prediction reference resampling, methods ofprocessing bitstream constraints relating to inter-layer predictiontypes, and related processes described in greater detail above and belowwith respect to FIGS. 4-5. As one example, inter-layer prediction unit75 may be configured to perform any or all of the techniques describedin this disclosure. However, aspects of this disclosure are not solimited. In some examples, the techniques described in this disclosuremay be shared among the various components of video decoder 30. In someexamples, additionally or alternatively, a processor (not shown) may beconfigured to perform any or all of the techniques described in thisdisclosure.

For purposes of explanation, this disclosure describes video decoder 30in the context of HEVC coding. However, the techniques of thisdisclosure may be applicable to other coding standards or methods. Thedecoder 30 of FIG. 3A illustrates a single layer of a codec. However, aswill be described further with respect to FIG. 3B, some or all of thevideo decoder 30 may be duplicated for processing according to amulti-layer codec.

In the example of FIG. 3A, video decoder 30 includes an entropy decodingunit 70, motion compensation unit 72, intra prediction unit 74,inter-layer prediction unit 75, inverse quantization unit 76, inversetransformation unit 78, reference frame memory 82 and summer 80. In someembodiments, motion compensation unit 72 and/or intra prediction unit 74may be configured to perform inter-layer prediction, in which case theinter-layer prediction unit 75 may be omitted. Video decoder 30 may, insome examples, perform a decoding pass generally reciprocal to theencoding pass described with respect to video encoder 20 (FIG. 2A).Motion compensation unit 72 may generate prediction data based on motionvectors received from entropy decoding unit 70, while intra-predictionunit 74 may generate prediction data based on intra-prediction modeindicators received from entropy decoding unit 70. Reference framememory 82 may include a decoded picture buffer. The decoded picturebuffer is a broad term having its ordinary meaning, and in someembodiments refers to a video codec-managed data structure of referenceframes.

During the decoding process, video decoder 30 receives an encoded videobitstream that represents video blocks of an encoded video slice andassociated syntax elements from video encoder 20. Entropy decoding unit70 of video decoder 30 entropy decodes the bitstream to generatequantized coefficients, motion vectors or intra-prediction modeindicators, and other syntax elements. Entropy decoding unit 70 forwardsthe motion vectors to and other syntax elements to motion compensationunit 72. Video decoder 30 may receive the syntax elements at the videoslice level and/or the video block level.

When the video slice is coded as an intra-coded (I) slice, intraprediction unit 74 may generate prediction data for a video block of thecurrent video slice based on a signaled intra prediction mode and datafrom previously decoded blocks of the current frame or picture. When thevideo frame is coded as an inter-coded (e.g., B, P or GPB) slice, motioncompensation unit 72 produces predictive blocks for a video block of thecurrent video slice based on the motion vectors and other syntaxelements received from entropy decoding unit 70. The predictive blocksmay be produced from one of the reference pictures within one of thereference picture lists. Video decoder 30 may construct the referenceframe lists, List 0 and List 1, using default construction techniquesbased on reference pictures stored in reference frame memory 82. Motioncompensation unit 72 determines prediction information for a video blockof the current video slice by parsing the motion vectors and othersyntax elements, and uses the prediction information to produce thepredictive blocks for the current video block being decoded. Forexample, motion compensation unit 72 uses some of the received syntaxelements to determine a prediction mode (e.g., intra- orinter-prediction) used to code the video blocks of the video slice, aninter-prediction slice type (e.g., B slice, P slice, or GPB slice),construction information for one or more of the reference picture listsfor the slice, motion vectors for each inter-encoded video block of theslice, inter-prediction status for each inter-coded video block of theslice, and other information to decode the video blocks in the currentvideo slice.

Motion compensation unit 72 may also perform interpolation based oninterpolation filters. Motion compensation unit 72 may use interpolationfilters as used by video encoder 20 during encoding of the video blocksto calculate interpolated values for sub-integer pixels of referenceblocks. In this case, motion compensation unit 72 may determine theinterpolation filters used by video encoder 20 from the received syntaxelements and use the interpolation filters to produce predictive blocks.

Video decoder 30 may also include an inter-layer prediction unit 75. Theinter-layer prediction unit 75 is configured to predict a current block(e.g., a current block in the EL) using one or more different layersthat are available in SVC (e.g., a base or reference layer). Suchprediction may be referred to as inter-layer prediction. Inter-layerprediction unit 75 utilizes prediction methods to reduce inter-layerredundancy, thereby improving coding efficiency and reducingcomputational resource requirements. Some examples of inter-layerprediction include inter-layer intra prediction, inter-layer motionprediction, and inter-layer residual prediction. Inter-layer intraprediction uses the reconstruction of co-located blocks in the baselayer to predict the current block in the enhancement layer. Inter-layermotion prediction uses motion information of the base layer to predictmotion in the enhancement layer. Inter-layer residual prediction usesthe residue of the base layer to predict the residue of the enhancementlayer. When the base and enhancement layers have different spatialresolutions, spatial motion vector scaling and/or inter-layer positionmapping may be performed by the inter-layer prediction unit 75 using atemporal scaling function, as described in greater detail below.

Inverse quantization unit 76 inverse quantizes, e.g., de-quantizes, thequantized transform coefficients provided in the bitstream and decodedby entropy decoding unit 70. The inverse quantization process mayinclude use of a quantization parameter QPY calculated by video decoder30 for each video block in the video slice to determine a degree ofquantization and, likewise, a degree of inverse quantization that shouldbe applied.

Inverse transform unit 78 applies an inverse transform, e.g., an inverseDCT, an inverse DST, an inverse integer transform, or a conceptuallysimilar inverse transform process, to the transform coefficients inorder to produce residual blocks in the pixel domain.

After motion compensation unit 72 generates the predictive block for thecurrent video block based on the motion vectors and other syntaxelements, video decoder 30 forms a decoded video block by summing theresidual blocks from inverse transform unit 78 with the correspondingpredictive blocks generated by motion compensation unit 72. Summer 90represents the component or components that perform this summationoperation. If desired, a deblocking filter may also be applied to filterthe decoded blocks in order to remove blockiness artifacts. Other loopfilters (either in the coding loop or after the coding loop) may also beused to smooth pixel transitions, or otherwise improve the videoquality. The decoded video blocks in a given frame or picture are thenstored in reference frame memory 82, which stores reference picturesused for subsequent motion compensation. Reference frame memory 82 alsostores decoded video for later presentation on a display device, such asdisplay device 32 of FIG. 1.

Multi-Layer Decoder

FIG. 3B is a block diagram illustrating an example of a multi-layervideo decoder 31 that may implement techniques in accordance withaspects described in this disclosure. The video decoder 31 may beconfigured to process multi-layer video frames, such as for SHVC andmultiview coding. Further, the video decoder 31 may be configured toperform any or all of the techniques of this disclosure.

The video decoder 31 includes a video decoder 30A and video decoder 30B,each of which may be configured as the video decoder 30 of FIG. 3A andmay perform the functions described above with respect to the videodecoder 30. Further, as indicated by the reuse of reference numbers, thevideo decoders 30A and 30B may include at least some of the systems andsubsystems as the video decoder 30. Although the video decoder 31 isillustrated as including two video decoders 30A and 30B, the videodecoder 31 is not limited as such and may include any number of videodecoder 30 layers. In some embodiments, the video decoder 31 may includea video decoder 30 for each picture or frame in an access unit. Forexample, an access unit that includes five pictures may be processed ordecoded by a video decoder that includes five decoder layers. In someembodiments, the video decoder 31 may include more decoder layers thanframes in an access unit. In some such cases, some of the video decoderlayers may be inactive when processing some access units.

In addition to the video decoders 30A and 30B, the video decoder 31 mayinclude an upsampling unit 92. In some embodiments, the upsampling unit92 may upsample a base layer of a received video frame to create anenhanced layer to be added to the reference picture list for the frameor access unit. This enhanced layer can be stored in the reference framememory 82 (e.g., in its decoded picture buffer, etc.). In someembodiments, the upsampling unit 92 can include some or all of theembodiments described with respect to the resampling unit 90 of FIG. 2A.In some embodiments, the upsampling unit 92 is configured to upsample alayer and reorganize, redefine, modify, or adjust one or more slices tocomply with a set of slice boundary rules and/or raster scan rules. Insome cases, the upsampling unit 92 may be a resampling unit configuredto upsample and/or downsample a layer of a received video frame

The upsampling unit 92 may be configured to receive a picture or frame(or picture information associated with the picture) from the decodedpicture buffer 82 of the lower layer decoder (e.g., the video decoder30A) and to upsample the picture (or the received picture information).This upsampled picture may then be provided to the mode select unit 71of a higher layer decoder (e.g., the video decoder 30B) configured todecode a picture in the same access unit as the lower layer decoder. Insome cases, the higher layer decoder is one layer removed from the lowerlayer decoder. In other cases, there may be one or more higher layerdecoders between the layer 0 decoder and the layer 1 decoder of FIG. 3B.

In some cases, the upsampling unit 92 may be omitted or bypassed. Insuch cases, the picture from the decoded picture buffer 82 of the videodecoder 30A may be provided directly, or at least without being providedto the upsampling unit 92, to the mode select unit 71 of the videodecoder 30B. For example, if video data provided to the video decoder30B and the reference picture from the decoded picture buffer 82 of thevideo decoder 30A are of the same size or resolution, the referencepicture may be provided to the video decoder 30B without upsampling.Further, in some embodiments, the upsampling unit 92 may be a resamplingunit 90 configured to upsample or downsample a reference picturereceived from the decoded picture buffer 82 of the video decoder 30A.

As illustrated in FIG. 3B, the video decoder 31 may further include ademultiplexor 99, or demux. The demux 99 can split an encoded videobitstream into multiple bitstreams with each bitstream output by thedemux 99 being provided to a different video decoder 30A and 30B. Themultiple bitstreams may be created by receiving a bitstream and each ofthe video decoders 30A and 30B receives a portion of the bitstream at agiven time. While in some cases the bits from the bitstream received atthe demux 99 may be alternated one bit at a time between each of thevideo decoders (e.g., video decoders 30A and 30B in the example of FIG.3B), in many cases the bitstream is divided differently. For example,the bitstream may be divided by alternating which video decoder receivesthe bitstream one block at a time. In another example, the bitstream maybe divided by a non-1:1 ratio of blocks to each of the video decoders30A and 30B. For instance, two blocks may be provided to the videodecoder 30B for each block provided to the video decoder 30A. In someembodiments, the division of the bitstream by the demux 99 may bepreprogrammed. In other embodiments, the demux 99 may divide thebitstream based on a control signal received from a system external tothe video decoder 31, such as from a processor on the destination device14. The control signal may be generated based on the resolution orbitrate of a video from the input interface 28, based on a bandwidth ofthe channel 16, based on a subscription associated with a user (e.g., apaid subscription versus a free subscription), or based on any otherfactor for determining a resolution obtainable by the video decoder 31.

Reference Layer Types

In an implementation of MV-HEVC and SHVC, there is adirect_dependency_flag syntax element specifying what layer can be usedfor inter-layer prediction. direct_dependency_flag[i][j] equal to 0specifies that the layer with index j is not a direct reference layerfor the layer with index i. direct_dependency_flag[i][j] equal to 1specifies that the layer with index j may be a direct reference layerfor the layer with index i. When direct_dependency_flag[i][j] is notpresent for i and j in the range of 0 to vps_max_layers minus1, it isinferred to be equal to 0.

In addition, two types of inter-layer prediction can be applied:inter-layer motion prediction, inter-layer sample prediction, or both.To specify what inter-layer prediction types are available for someparticular layer, the direct_dependency_type is signaled.

direct_dependency_type[i][j] is used to derive the variablesNumSamplePredRefLayers [i], NumMotionPredRefLayers[i],SamplePredEnabledFlag[i][j], and MotionPredEnabledFlag[i][j]. Thevariable NumSamplePredRefLayers[i] can refer to the number of referencelayers that can be used for sample prediction for the layer with indexi. The variable NumMotionPredRefLayers[i] can refer to the number ofreference layers that can be used for motion prediction for the layerwith index i. The variable SamplePredEnabledFlag[i][j] can refer towhether sample prediction using the layer with index j is enabled forthe layer with index i. The variable MotionPredEnabledFlag[i][j] canrefer to motion prediction using the layer with index j is enabled forthe layer with index i. direct_dependency_type[i][j] should be in therange of 0 to 2, inclusive, in bitstreams. Although the value ofdirect_dependency_type[i][j] should be in the range of 0 to 2,inclusive, decoders should allow values of direct_dependency_type[i][j]in the range of 3 to 2³²-2, inclusive, to appear in the syntax.

The variables NumSamplePredRefLayers[i], NumMotionPredRefLayers[i],SamplePredEnabledFlag[i][j], MotionPredEnabledFlag[i][j],NumDirectRefLayers[i], RefLayerId[i][j], MotionPredRefLayerId[i][j], andSamplePredRefLayerId[i][j] are derived as follows:

for( i = 0; i < 64; i++ ) {   NumSamplePredRefLayers[ i ] = 0  NumMotionPredRefLayers[ i ] = 0   NumDirectRefLayers[ i ] = 0   for( j= 0; j < 64; j++ ) {     SamplePredEnabledFlag[ i ][ j ] = 0    MotionPredEnabledFlag[ i ][ j ] = 0     RefLayerId[ i ][ j ] = 0    SamplePredRefLayerId[ i ][ j ] = 0     MotionPredRefLayerId[ i ][ j] = 0   } } for( i = 1; i <= vps_max_layers_minus1; i++ ) {   iNuhLId =layer_id_in_nuh[ i ]   for( j = 0; j < i; j++ )     if(direct_dependency_flag[ i ][ j ] ) {       RefLayerId[ iNuhLId ][NumDirectRefLayers       [ iNuhLId ]++ ] =     layer_id_in_nuh[ j ]      SamplePredEnabledFlag[ iNuhLId ][ j ] = ( (    direct_dependency_type[ i ][ j ] + 1 ) & 1 )      NumSamplePredRefLayers[ iNuhLId ] +=     SamplePredEnabledFlag[iNuhLId ][ j ]       MotionPredEnabledFlag[ iNuhLId ][ j ] = ( ( (    direct_dependency_type[ i ][ j ] + 1 ) & 2 ) >> 1 )      NumMotionPredRefLayers[ iNuhLId ] +=     MotionPredEnabledFlag[iNuhLId ][ j ]   } } for( i = 1, mIdx = 0, sIdx = 0; i <=vps_max_layers_minus1; i++ ) {   iNuhLId = layer_id_in_nuh[ i ]   for( j= 0, j < i; j++ ) {     if( MotionPredEnabledFlag[ iNuhLId ][ j ] )      MotionPredRefLayerId[ iNuhLId ][ mIdx++ ] =       layer_id_in_nuh[j ]     if( SamplePredEnabledFlag[ INuhLid ][ j ] )      SamplePredRefLayerId[ iNuhLid ][ sIdx++ ] =       layer_id_in_nuh[j ]   } }Restriction on Number of Pictures Used for Inter-Layer Reference withResampling

In one SHVC implementation, the number of inter-layer reference picturethat needs to be resampled for decoding of any particular picture islimited to be up to one. Resampling process, for example, is invokedwhen the reference and enhancement layer have different picture sizes.

However, having a limit on the number of inter-layer reference picturethat is resampled may create problems, such as the following:

-   -   When decoding a current picture, a picture that is only used for        inter-layer motion prediction (not for sample prediction) is        also resampled when it has a different spatial resolution than        the current picture. However, resampling of such a picture may        waste computing resource unnecessarily.    -   If a picture that is only used for inter-layer motion prediction        exists when decoding a current picture, then no other pictures        for inter-layer sample prediction can be sample-resampled        according to the restriction that the number of pictures used        for inter-layer reference with resampling cannot be greater than        one. In other words, when such a picture exists, if there is no        other lower-layer picture that has the same resolution as the        current picture, inter-layer prediction of samples cannot be        used for the current picture even if there is another low-layer        picture with a different spatial resolution.    -   Bitstream conformance restrictions are missing for pictures of        certain direct reference layers that are indicated as not used        for inter-layer sample prediction or indicated as not used for        inter-layer motion prediction.    -   Pictures for inter-layer reference are included into the initial        reference picture lists (before reference picture list        modification commands) without making a difference between        different types of inter-layer predictions indicated for the        pictures, which is sub-optimal.    -   Coding of collocated_ref_idx signaled in the slice header and        the reference index signaled at block (e.g., CU, PU, etc.) level        may use unnecessarily more bits.

Inter-Layer Prediction Types in Multi-Layer Video Coding

In order to address these and other challenges, the techniques accordingto certain aspects can independently control the number of referencepictures to be resampled for inter-layer motion prediction and thenumber of reference pictures to be resampled for inter-layer sampleprediction. The techniques can also provide and/or process bitstreamconstraints relating to inter-layer prediction types. More specifically,the techniques can provide and/or process a bitstream constraint thatthe collocated reference index (e.g., collocated_ref_idx) can only referto an ILRP used for at least ILMP. The techniques can also provideand/or process a bitstream constraint that reference index (e.g.,ref_idx) can only refer to an ILRP used for at least ILSP.

In this manner, when decoding a current picture, an ILRP only used inILMP does not need to be sample-resampled. Also, an ILRP only used inILMP does not have to prevent another ILRP from being used in ILP. Forexample, an ILRP used in ILSP can be sample-resampled and used in ILP.This can lead to more accurate prediction and more efficient coding. Forexample, one more type of ILP (e.g., ILSP in the example above) can beused. In addition, computational complexity can be reduced by avoidinginvoking unnecessary resampling processes. Certain details relating tothe techniques are described below.

Pictures Indicated as not Used for Inter-Layer Sample Prediction

According to certain aspects, the techniques can exclude an inter-layerreference picture from the resampling process if it is indicated to beused only for inter-layer motion prediction. For this type of pictures,sample (pixel) information does not need to be stored in the memory.

In addition, an inter-layer reference picture indicated to be used onlyfor inter-layer motion prediction is not counted as a picture thatrequires sample-resampling process, since samples will not be used forinter prediction purpose. Consequently, another low-layer picture with adifferent spatial resolution can be used for inter-layer prediction ofsamples for the current picture.

Moreover, a picture that is indicated as not used for inter-layer sampleprediction may not be referred to by a reference index signaled at block(e.g., CU, PU, etc.) level. For example, such picture cannot be used forinter-prediction.

Furthermore, the total number of reference pictures used in referenceindex signaling can be adjusted, including only the pictures that can beused for inter prediction, such that the reference index signaled inblock (e.g., CU, PU, etc.) level can use fewer bits.

Pictures Indicated as not Used for Inter-Layer Motion Prediction

According to certain aspects, for a picture indicated not to be used forinter-layer motion prediction (e.g., indicated to be used only forinter-layer sample prediction), the motion information is not requiredto be derived and this picture cannot be used for temporal motion vector(TMVP) derivation. For example, such picture cannot be used as acollocated picture in TMVP derivation. And motion information may not bestored for this picture.

It can be implied that a collocated picture, for example, defined bycollocated_ref_idx syntax element, cannot be a picture that is indicatednot used for inter-layer motion prediction. In other words,collocated_red_idx should not point to a lower-layer picture that isonly for inter-layer sample prediction or that is not used forinter-layer prediction at all.

In addition, the total number of reference pictures used to define thecollocated_ref_idx range can be adjusted to include only the picturesthat can be used for TMVP derivation, such that the signaling ofcollocated_ref_idx can use fewer bits.

Alternative to not using this type of reference picture as a collocatedpicture, default motion information can be assigned to the inter-layersample only prediction pictures. The default motion information caninclude at least prediction mode, motion vectors, reference indices, andreference picture picture order counts (POCs). For example, intraprediction mode, which specifies no motion information, can be assignedfor the inter-layer sample only prediction picture. In such case, noTMVP may be derived if this picture is used as a collocated picture dueto intra prediction mode being assigned. Accordingly, default motioninformation may be assigned.

Separate Constraint on Number of Sample Resampled and Motion ResampledInter-Layer Pictures

In one embodiment, inter-layer reference pictures used for inter-layermotion prediction are counted separately from the inter-layer sampleprediction towards the constraint on the number of the resampledpictures. In early versions of SHVC, only one resampled picture could beused; sample-resampled and motion-resampled pictures were not countedseparately, and as a result, only one ILP type (e.g., ILMP only or ILSPonly) could be used in some cases, as mentioned above. If thesample-resampled and motion-resampled pictures are counted separately,then up to one sample resampling can be applied, and up to one motionresampling can be applied.

In another embodiment, the number of sample resampled inter-layerpictures and the number of motion resampled inter-layer pictures can berestricted and/or limited separately with a different number. Forexample, one sample resampled inter-layer picture and two motionresampled inter-layer pictures can be restricted to be used.

The above mentioned techniques can be implemented as shown in thefollowing examples. The examples are provided in the context of earlyversions of SHVC. Changes from the early versions of SHVC are indicatedin italics. In certain embodiments, the techniques may not count thepicture used only for inter-layer motion prediction towards resampledpictures number.

Example 1

TABLE 1 Example 1   G.8.1.2 Decoding process for inter-layer referencepicture set     Output of this process is an updated list of  inter-layer reference pictures RefPicSetInterLayer.     The listRefPicSetInterLayer is first emptied and then   derived as follows.  for( i = 0; i < NumActiveRefLayerPics; i++ ) {   if( there is apicture picX in the DPB that is in the same access unit as the currentpicture and has nuh_layer_id equal to RefPicLayerId[ i ] ) {     IfSamplePredEnabledFlag[nuh_layer_id]   [ RefPicLayerId[ i ]] is equal to0 the following applies     - the picture motion field resamplingprocess as specified in   subclause G.8.1.4.2 is invoked withrlPicMotion as input, and with the   resampled motion field ofrsPicMotion as output, where the variable   rlPicMotion is defined as agroup of variable arrays specifying the   compressed motion field ofrlPic and the variable rsPicMotion is   defined as a group of variablearrays specifying the resampled   motion field of rsPic.   Otherwise,    - an interlayer reference picture rsPic is derived by invoking the  subclause G.8.1.4 with picX given as input     RefPicSetInterLayer[ i] = rsPic     RefPicSetInterLayer[ i ] is marked as “used for long-term    reference”   } else     RefPicSetInterLayer[ i ] = “no referencepicture” }   There should be no entry equal to “no reference picture” inRefPicSetInterLayer.

In Example 1, the motion-resampling process is called separately fromthe sample-resampling process where ILRP is used for ILMP only. In thisexample, when ILRP picture is used for both ILMP and ILSP,motion-resampling process is invoked through the sample-resamplingprocess. An alternative description is provided in Example 2. In theexamples and description above and below, portions in italics mayindicate changes to the early versions of SHVC. Portions in underlinemay indicate portions that are specific for SHVC only and not present inthe MV-HEVC.

Example 2

In Example 2, an alternative description is provided where the twoprocesses (e.g., motion-resampling and sample-resampling) are calledindependently depending on whether ILRP is used for ILMP and/or ILSP.The invocation of the motion-resampling process is removed from thesample-resampling in the section G.8.1.4 and moved to a separate sectionG.8.1.5, for example, in order to improve readability of thespecification text.

TABLE 2 Example 2    G.8.1.2 Decoding process for inter-layer referencepicture set    Output of this process is an updated list of inter-layerreference pictures RefPicSetInterLayer.    The list RefPicSetInterLayeris first emptied and then derived as follows.       for( i = 0; i <NumActiveRefLayerPics; i++ ) {     if( there is a picture picX in theDPB that is in the same access unit as the current picture and    has      nuh_layer_id equal to RefPicLayerId[ i ] ) {       if(MotionPredEnabledFlag[ nuh_layer_id ][ RefPicLayerId[ i ] ] )        amotion resampled field rsPicMotion of an interlayer reference picturersPic is    derived by invoking subclause G.8.1.5 with the compressedmotion field of picX as input       if( SamplePredEnabledFlag[nuh_layer_id ][ RefPicLayerId[ i ] ] )        a sample resampledrsPicSample of an interlayer reference picture rsPic is derived   by invoking the subclause G.8.1.4 with the samples of picX and   DirectRefLayerIdx[ currLayerId ][ RefPicLayerId[ i ] ] as inputs     RefPicSetInterLayer[ i ] = rsPic      RefPicSetInterLayer[ i ] ismarked as “used for long-term reference”     } else     RefPicSetInterLayer[ i ] = “no reference picture”    }    Thereshall be no entry equal to “no reference picture” inRefPicSetInterLayer.    If the current picture is a RADL picture, thereshall be no entry in the RefPicSetInterLayer that is a RASL picture.G.8.1.4 Resampling process for inter layer reference pictures    Inputto this process is a decoded reference layer picture rlPic.    Output ofthis process is the resampled reference layer picture rsPic.    Thevariables PicWidthInSamplesL and PicHeightInSamplesL are set equal topic_width_in_luma_samples and pic_height_in_luma_samples, respectively.The variable rsPicSample is defined as a group of sample arraysspecifying the resampled sample values of rsPic of the luma and chromacomponents. The variable rsPicMotion is defined as a group of variablearrays specifying the resampled motion field of rsPic.    The variablesRefLayerPicWidthInSamplesL and RefLayerPicHeightInSamplesL are set equalto the width and height of the decoded reference layer picture rlPic inunits of luma samples, respectively. The variable rlPicSample is definedas a group of sample arrays specifying the sample values of rlPic of theluma and chroma components. The variable rlPicMotion is defined as agroup of variable arrays specifying the compressed motion field ofrlPic.      The variables PicWidthInSamplesC, PicHeightInSamplesC,RefLayerPicWidthInSamplesC, and RefLayerPicHeightInSamplesC are derivedas follows:    PicWidthInSamplesC = PicWidthInSamplesL / subWidthC   PicHeightInSamplesC = PicHeightInSamplesL / subHeightC (G-11)   RefLayerPicWidthInSamplesC = RefLayerPicWidthInSamplesL / subWidthC(G-12)    RefLayerPicHeightInSamplesC = RefLayerPicHeightInSamplesL /subHeightC (G-13)      The variables ScaledRefLayerLeftOffset,ScaledRefLayerTopOffset, ScaledRefLayerRightOffset andScaledRefLayerBottomOffset are derived as follows:     ScaledRefLayerLeftOffset = scaled_ref_layer_left_offset << 1 (G-14)     ScaledRefLayerTopOffset = scaled_ref_layer_top_offset << 1 (G-15)     ScaledRefLayerRightOffset = scaled_ref_layer_right_offset << 1(G-16)      ScaledRefLayerBottomOffset = scaled_ref_layer_bottom_offset<< 1 (G-17)      The variables ScaledRefLayerPicWidthInSamplesL andScaledRefLayerPicHeightInSamplesL are derived as follows:     ScaledRefLayerPicWidthInSamplesL = PicWidthInSamplesL −        ScaledRefLayerLeftOffset − ScaledRefLayerRightOffset (G-18)     ScaledRefLayerPicHeightInSamplesL = PicHeightInSamplesL −        ScaledRefLayerTopOffset − ScaledRefLayerBottomOffset (G-19)     The variables ScaleFactorX and ScaleFactorY are derived as follows:       ScaleFactorX = ( ( RefLayerPicWidthInSamplesL <<         16 ) + (ScaledRefLayerPicWidthInSamplesL >> 1 ) ) /         Scaled RefLayerPicWidthInSamplesL (G-20)        ScaleFactorY = ( (RefLayerPicHeightlnSamplesL <<         16 ) + (ScaledRefLayerPicHeightInSamplesL >> 1 ) ) /         ScaledRefLayerPicHeightInSamplesL (G-21)      The following steps are applied toderive the resampled inter layer reference picture rsPic. -    ifPicWidthInSamplesL is equal to RefLayerPicWidthInSamplesL andPicHeightInSamplesL is    equal to RefLayerPicHeightInSamplesL and thevalues of ScaledRefLayerLeftOffset,    ScaledRefLayerTopOffset,ScaledRefLayerRightOffset and ScaledRefLayerBottomOffset are all   equal to 0    -   rsPicSample is set equal to rlPicSample,   -   When alt_collocated_indication_flag is equal to 1, rsPicMotion isset equal to rlPicMotion. -    otherwise, rsPic is derived as follows:   -   The picture sample resampling process as specified in subclauseG.8.1.4.1 is invoked with the      sample values of rlPicSample asinput, and with the resampled sample values of rsPicSample     asoutput.     

    

    

 G.8.1.5 Resampling process of picture motion field    Input to thisprocess is rlPicMotion specifying the motion field of the picture rlPic.   Output of this process is rsPicMotion specifying the resampled motionfield of the resampled picture.    The motion field of rlPic specifiedby rlPicMotion consists of: -   a ( RefLayerPicWidthInSamplesL ) × (RefLayerPicHeightInSamplesL ) array predModeRL   specifies theprediction modes of the reference layer picture rlPic, -   two (RefLayerPicWidthInSamplesL ) × ( RefLayerPicHeightInSamplesL ) arraysrefIdxLXRL   specify the reference indices of the reference layerpicture rlPic, with X = 0,1, -   two ( RefLayerPicWidthInSamplesL ) × (RefLayerPicHeightInSamplesL ) arrays mvLXRL specify   the luma motionvectors of the reference layer picture rlPic, with X = 0,1, -   two (RefLayerPicWidthInSamplesL ) × ( RefLayerPicHeightInSamplesL ) arrays  refPicOrderCntLXRL specify the reference picture order counts of thereference layer picture rlPic,   with X = 0, 1, -   two (RefLayerPicWidthInSamplesL ) × ( RefLayerPicHeightInSamplesL ) arrayspredFlagLXRL   specify the prediction list utilization flags of thereference layer picture rlPic, with X = 0,1.    The resampled motionfield specified by rsPicMotion consists of:    -   a (PicWidthInSamplesL ) × ( PicHeightInSamplesL ) array predMode specifiesthe prediction modes of the resampled picture,    -   two (PicWidthInSamplesL ) × ( PicHeightInSamplesL ) arrays refIdxLX specifythe reference indexes of the resampled picture, with X = 0,1,    -   two( PicWidthInSamplesL ) × ( PicHeightInSamplesL ) arrays mvLX specify theluma motion vectors of the resampled picture, with X = 0,1,    -   two (PicWidthInSamplesL ) × ( PicHeightInSamplesL ) arrays refPicOrderCntLXspecify the reference picture order counts of the resampled picture,with X = 0, 1 -   two ( PicWidthInSamplesL ) × ( PicHeightInSamplesL )arrays predFlagLX specify the prediction   list utilization flags of theresampled picture, with X = 0,1.    For each luma sample location xPb =0 ... ( ( PicWidthInSamplesL + 15 ) >> 4 ) − 1 and yPb = 0 . . . ( (PicHeightInSamplesL + 15 ) >> 4) − 1,    -   The variables xP and yP areset to ( xPb << 4 ) and ( yPb << 4 ), respectively,    -   The variablespredMode[xP][yP], refIdxLX[xP][yP], mvLX[xP][yP] and     refPicOrderCntLX[xP][yP], and predFlagLX[xP][yP], with X = 0,1, ofthe resampled      picture are derived by invoking inter layer motionderivation process specified in      subclause G.8.1.4.2.1 with the lumalocation ( xP, yP ), predModeRL, refIdxLXRL,      mvLXRL,refPicOrderCntLXRL, and predFlagLXRL, with X = 0,1, given as input.

 G.8.1.5.1 Derivation process for inter layer motion    Inputs to thisprocess are -   a luma location ( xP, yP) specifying the top-left sampleof the current luma prediction block   relative to the top-left lumasample of the current picture, -   the reference layer predictionmodearray predModeRL, -   the reference layer reference index arraysrefIdxL0RL and refIdxL1RL -   the reference layer motion vector arraysmvL0RL and mvL1RL -   the reference layer reference picture order countsarrays refPicOrderCntL0RL and   refPicOrderCntL1RL -   the referencelayer prediction list utilization flag arrays predFlagL0RL andpredFlagL1RL.    Outputs of this process are -   a derived predictionmode predMode, -   two derived motion vectors mvL0 and mvL1 -   twoderived reference indices refIdxL0 and refIdxL1 -   two derivedreference picture order counts refPicOrderCntL0 and refPicOrderCntL1-   two derived prediction list utilization flags predFlagL0 andpredFlagL1.    The variables predMode, mvLX, refIdxLX, refPicOrderCntLX,and predFlagLX are derived as follows.   1.  The center location (xPCtr,yPCtr) of the luma prediction block is derived as follows          xPCtr = xP + 8 (G-39)           yPCtr = yP + 8 (G-40)  2.  The derivation process for reference layer luma sample locationspecified in subclause      G.6.1 is invoked with luma location ( xPCtr, yPCtr ) given as the inputs and      ( xRef , yRef ) as output.  3.  The collocated position (xRL, yRL) is derived as follows          xRL = ( xRef >> 4 ) << 4 (G-41)           yRL = ( yRef >> 4 )<< 4 (G-42)   4.  The reference layer motion vector is derived asfollows      -   If ( xRL < 0 ) or ( xRL >= RefLayerPicWidthInSamplesL )or ( yRL < 0 ) or        ( yRL >= RefLayerPicHeightInSamplesL ),predMode[ xP ][ yP ] is set to         MODE_INTRA.      -   Otherwise,predMode[ xP ][ yP ] is derived as follows            predMode[ xP ][ yP] = predModeRL[ xRL ][ yRL ] (G-43)      -   If predMode[ xP ][ yP ] isequal to MODE_INTER, for each X = 0, 1, the following         applies        refIdxLX[ xP ][ yP ] = refIdxLXRL[ xRL ][ yRL ] (G-44)        refPicOrderCntLX[ xP ][ yP ] = refPicOrderCntLXRL[ xRL ][ yRL ](G-45)         predFlagLX[ xP ][ yP ] = predFlagLXRL[ xRL ][ yRL ](G-46)       -   If ScaledRefLayerPicWidthInSamplesL is not equal to         RefLayerPicWidthInSamplesL, mvLX[ xP ][ yP ][ 0 ] is derived asfollows:            scaleFactorMVX =         Clip3( −4096, 4095, ( (ScaledRefLayerPicWidthInSamplesL         << 8 ) + (RefLayerPicWidthInSamplesL >> 1 ) ) /        RefLayerPicWidthInSamplesL) (G-47)         mvLX[ xP ][ yP ][0] =Clip3( −32768, 32767, Sign(scaleFactorMVX *          mvLXRL[ xRL ][ yRL][ 0 ] ) *             ( ( Abs ( scaleFactorMVX * mvLXRL[ xRL ][ yRL ][0 ] ) +           127 ) >> 8 ) ) (G-48)        -  Otherwise,        mvLX[ xP ][ yP ][ 0 ] = mvLXRL[ xRL ][ yRL ][ 0 ] (G-49)       -  If ScaledRefLayerPicHeightInSamplesL is not equal to         RefLayerPicHeightInSamplesL, mvLX[ xP ][ yP ][ 1 ] is derivedas follows:         scaleFactorMVY = Clip3( −4096, 4095, ( (ScaledRefLayerPicHeightInSamplesL <<          8 ) + (RefLayerPicHeightInSamplesL >> 1 ) ) /         RefLayerPicHeightInSamplesL) (G-50)         mvLX[ xP ][ yP ][ 1] = Clip3( −32768, 32767, Sign(scaleFactorMVY *          mvLXRL[ xRL ][yRL ][ 1 ] ) * ( ( Abs          ( scaleFactorMVY * mvLXRL[ xRL ][ yRL ][1 ] ) +           127 ) >> 8 ) ) (G-51)        -  Otherwise,          mvLX[ xP ][ yP ][ 1 ] = mvLXRL[ xRL ][ yRL ][ 1 ] (G-52)     -   Otherwise, if predMode[ xP ][ yP ] is equal to MODE_INTRA       -  both components of mvL0[ xP ][ yP ] and mvL1[ xP ][ yP ] areset to 0,          refIdxL0[ xP ][ yP ] and refIdxL1[ xP ][ yP ] are setto −1,          refPicOrderCntL0[ xP ][ yP ] and refPicOrderCntL1[ xP ][yP ] are set to −1,          predFlagL0[ xP ][ yP ] and predFlagL1[ xP][ yP ] are set to 0. G.11.1.3 Scalable Main profile    Bitstreamsconforming to the scalable main profile shall obey the followingconstraints: -   The picture resampling process as specified insubclauses G.8.1.4. shall not be invoked more than    once for decodingof each particular picture. -   The resampling process of picture motionfield as specified in subclause G.8.1.5 shall not be   invoked more thanonce for decoding of each particular picture. -   Whenavc_base_layer_flag equal to 1, it is a requirement of bitstreamconformance that   MotionPredRefLayerId[ iNuhLId ][ mIdx ] shall not beequal to 0 for iNuhLId equal to any value of   nuh_layer_id present inthe bitstream and any value of mIdx in the range of 0 to  NumMotionPredRefLayers[ iNuhLId ] − 1, inclusive.

Bitstream Constraints

As explained above, the techniques can also provide and/or processbitstream constraints relating to inter-layer prediction types. The termor expression “bitstream constraint” is a broad term and/or expressionintended to have its broadest ordinary meaning. In one embodiment, abitstream constraint can refer to a rule that an encoder or a decodershould follow to be compliant with a certain standard. For example, theconformant to a certain standard bitstream should not contain elements(e.g., syntax elements) that violate the constraint. In the case of aconstraint violation, the bitstream is treated as not conformant and maynot be decoded by a decoder.

More specifically, the techniques can provide and/or process a bitstreamconstraint that the collocated reference index (e.g.,collocated_ref_idx) can only refer to an ILRP used for at least ILMP.The techniques can also provide and/or process a bitstream constraintthat reference index (e.g., ref_idx) can only refer to an ILRP used forat least ILSP. In some embodiments, the bitstream constraints can bedefined as follows. For example,

-   -   collocated_ref_idx specifies the reference index of the        collocated picture used for temporal motion vector prediction.        -   When slice_type is equal to P or when slice_type is equal to            B and collocated_from_l0 is equal to 1, collocated_ref_idx            refers to a picture in list 0, and the value of            collocated_ref_idx should be in the range of 0 to            num_ref_idx_l0_active_minus1, inclusive.        -   When slice_type is equal to B and collocated_from_l0 is            equal to 0, collocated_ref_idx refers to a picture in list            1, and the value of collocated_ref_idx should be in the            range of 0 to num_ref_idx_l1_active_minus1, inclusive.        -   It is a requirement of bitstream conformance that the            picture referred to by collocated_ref_idx should be the same            for all slices of a coded picture.        -   Let refLayerId be the value of nuh_layer_id of the picture            referred to by collocated_ref_idx, and currLayerId be the            value of nuh_layer_id of the current picture. It is a            requirement of bitstream conformance that            MotionPredEnabledFlag[currLayerId][refLayerId] should be            equal to 1.    -   ref_idx_l0[x0][y0] specifies the list 0 reference picture index        for the current prediction unit. The array indices x0, y0        specify the location (x0, y0) of the top-left luma sample of the        considered prediction block relative to the top-left luma sample        of the picture.        -   When ref_idx_l0[x0][y0] is not present it is inferred to be            equal to 0.        -   Let refLayerId be the value of nuh_layer_id of the picture            referred to by ref_idx_l0[x0][y0], and currLayerId be the            value of nuh_layer_id of the current picture. It is a            requirement of bitstream conformance that            SamplePredEnabledFlag[currLayerId][refLayerId] should be            equal to 1.        -   ref_idx_l1[x0][y0] has the same semantics as ref_idx_l0,            with l0 and list 0 replaced by l1 and list 1, respectively.

Certain details relating to the techniques are explained below inreference to FIG. 4 and FIG. 5. Various term used throughout thisdisclosure are broad terms having their ordinary meaning. In addition,in some embodiments, certain terms relate to the following videoconcepts. A picture can refer to video picture as that term is used incurrent standards (e.g., HEVC, SHVC). Methods described with respect toFIG. 4 and FIG. 5 may be implemented by computing hardware. In someembodiments, computing hardware can include one or computing devicescomprising computer hardware.

Method for Independent Control of Interlayer Motion Prediction ReferenceResampling and Interlayer Sample Prediction Reference Resampling

FIG. 4 is a flowchart illustrating an example method for independentcontrol of inter-layer motion prediction reference resampling andinter-layer sample prediction reference resampling, according to aspectsof this disclosure. The process 400 may be performed by an encoder(e.g., the encoder as shown in FIG. 2A, 2B, etc.), a decoder (e.g., thedecoder as shown in FIG. 3A, 3B, etc.), or any other component,depending on the embodiment. The blocks of the process 400 are describedwith respect to the decoder 31 in FIG. 3B, but the process 400 may beperformed by other components, such as an encoder, as mentioned above.The layer 1 video decoder 30B of the decoder 31 and/or the layer 0decoder 30A of the decoder 31 may perform the process 400, depending onthe embodiment. All embodiments described with respect to FIG. 4 may beimplemented separately, or in combination with one another. Certaindetails relating to the process 400 are explained above.

The process 400 starts at block 401. The decoder 31 can include a memory(e.g., reference frame memory 82) for storing video information.

At block 402, the decoder 31 identifies a current picture to bepredicted using at least one type of inter layer prediction (ILP), thetype of ILP comprising one or more of inter layer motion prediction(ILMP) or inter layer sample prediction (ILSP).

At block 403, the decoder 31 controls: (1) a number of pictures that maybe resampled and used to predict the current picture using ILMP and (2)a number of pictures that may be resampled and used to predict thecurrent picture using ILSP. The number of pictures that may be resampledand used to predict the current picture using ILMP can be controlledindependent of the number of pictures that may be resampled and used topredict the current picture using ILSP. For example, the decoder 31 cancontrol the number of pictures that may be resampled and used to predictthe current picture using ILMP independent of the number of picturesthat may be resampled and used to predict the current picture usingILSP.

The term or expression “controlled independent,” “independent control,”or variations thereof is a broad term and/or expression intended to haveits broadest ordinary meaning. To facilitate discussion, the term orexpression “independent control” will be used in the followingdescription. In one embodiment, independent control can refer toaffecting or setting the number of pictures that may be resampled andused to predict the current picture using ILMP without affecting orsetting the number of pictures that may be resampled and used to predictthe current picture using ILSP, and vice versa.

In another embodiment, independent control can refer to having aseparate limit for the number of pictures that may be resampled and usedto predict the current picture using ILMP and the number of picturesthat may be resampled and used to predict the current picture usingILSP. The limit on the number of pictures that may be resampled and usedto predict the current picture using ILMP and the number of picturesthat may be resampled and used to predict the current picture using ILSPcan be the same or different, depending on the embodiment. In yetanother embodiment, independent control can refer to not counting apicture that may be resampled (e.g., sample-resampled, motion-resampled,or both) and used to predict the current picture using ILMP towards thelimit on the number of pictures that may be resampled and used topredict the current picture using ILP.

In some embodiments, the number of pictures that may be resampled andused to predict the current picture using ILMP and the number ofpictures that may be resampled and used to predict the current pictureusing ILSP are the same (e.g., both are equal to 1). In otherembodiments, the number of pictures that may be resampled and used topredict the current picture using ILMP and the number of pictures thatmay be resampled and used to predict the current picture using ILSP aredifferent.

In certain embodiments, the decoder 31 predicts the current pictureusing at least one resampled picture. The at least one resampled picturecan be used to predict the current picture using ILMP, ILSP, or both,depending on the embodiment.

The process 400 ends at block 404. Blocks may be added and/or omitted inthe process 400, depending on the embodiment, and blocks of the process400 may be performed in different orders, depending on the embodiment.Any features and/or embodiments described with respect to resampling inthis disclosure may be implemented separately or in any combinationthereof. For example, any features and/or embodiments described inconnection with FIG. 4 may be implemented in any combination with anyfeatures and/or embodiments described in connection with FIG. 5, andvice versa.

Method for Processing Bitstream Constraints Relating to Inter-LayerPrediction Types

FIG. 5 is a flowchart illustrating an example method for processingbitstream constraints relating to inter-layer prediction types. Theprocess 500 may be performed by an encoder (e.g., the encoder as shownin FIG. 2A, 2B, etc.), a decoder (e.g., the decoder as shown in FIG. 3A,3B, etc.), or any other component, depending on the embodiment. Theblocks of the process 500 are described with respect to the encoder 21in FIG. 3B, but the process 500 may be performed by other components,such as a decoder, as mentioned above. The layer 1 video encoder 20B ofthe encoder 21 and/or the layer 0 encoder 20A of the encoder 21 mayperform the process 500, depending on the embodiment. All embodimentsdescribed with respect to FIG. 5 may be implemented separately, or incombination with one another. Certain details relating to the process500 are explained above, e.g., with respect to FIG. 4.

The process 500 starts at block 501. The encoder 21 can include a memory(e.g., reference frame memory 82) for storing video information.

At block 502, the encoder 21 identifies a current picture to bepredicted using at least one type of inter layer prediction (ILP). Thetype of ILP can include inter layer motion prediction (ILMP), or interlayer sample prediction (ILSP), or both.

At block 503, the encoder 21, when the current picture is to bepredicted using at least ILMP, processes a collocated reference indexvalue associated with the current picture, wherein the collocatedreference index value indicates a first reference picture that is usedin predicting the current picture using ILP. In some embodiments, thecollocated reference index value can refer to the value of thecollocated reference index. In certain embodiments, the collocatedreference index can also be referred to as the collocated referenceindex value.

At block 504, the encoder 21 determines whether the first referencepicture indicated by the collocated reference index value is enabled forILMP. For example, the encoder 21 can determine whether the firstreference picture is enabled for ILMP when the current picture is to bepredicted using at least ILMP. In some embodiments, the encoder 21determines whether the first reference picture is enabled for ILMP bydetermining a value of the motion prediction enabled flag for the firstreference picture. For example, the encoder 21 can determine that thefirst reference picture is enabled for ILMP when the motion predictionenabled flag value is equal to 1. In another example, the encoder 21 candetermine that the first reference picture is not enabled for ILMP whenthe motion prediction enabled flag value is equal to 0. In otherembodiments, other values of the motion prediction enabled flag valuecan be used to determine whether the first reference picture is enabledfor ILMP or not (e.g., equal to 2, 3, etc.).

At block 505, the encoder 21, when the current picture is to bepredicted using at least ILSP, processes a reference index valueassociated with a block in the current picture, wherein the referenceindex value indicates a second reference picture that is used inpredicting the block in the current picture using ILP. In someembodiments, the reference index value can refer to the value of thereference index. In certain embodiments, the reference index can also bereferred to as the reference index value.

At block 506, the encoder 21 determines whether the second referencepicture indicated by the reference index value is enabled for ILSP. Forexample, the encoder 21 can determine whether the second referencepicture is enabled for ILSP when the current picture is to be predictedusing at least ILSP. In some embodiments, the encoder 21 determineswhether the second reference picture is enabled for ILMP by determininga value of the sample prediction enabled flag for the first referencepicture. For example, the encoder 21 can determine that the secondreference picture is enabled for ILSP when the sample prediction enabledflag value is equal to 1. In another example, the encoder 21 candetermine that the second reference picture is not enabled for ILSP whenthe sample prediction enabled flag value is equal to 0. In otherembodiments, other values of the sample prediction enabled flag valuecan be used to determine whether the second reference picture is enabledfor ILSP or not (e.g., equal to 2, 3, etc.).

In certain embodiments, the encoder 21 signals the collocated referenceindex value in a bitstream when the first reference picture is enabledfor ILMP, or signal the reference index value in the bitstream when thesecond reference picture is enabled for ILSP, or both. For example, theencoder 21 signals only the collocated reference index value thatindicates a reference picture that is enabled for ILMP. Or the encoder21 signals the reference index value that indicates a reference picturethat is enabled for ILSP. Or the encoder 21 can do both. In this manner,only the index values that reference the corresponding type of referencepicture (e.g., ILMP enabled for collocated reference index, ILSP enabledfor reference index, etc.) may be signaled in the bitstream.

In some embodiments, the first reference picture and the secondreference picture may be the same. For example, a reference picture maybe used for both ILMP and ILSP (e.g., have both motion information andsamples).

The process 500 ends at block 507. Blocks may be added and/or omitted inthe process 500, depending on the embodiment, and blocks of the process500 may be performed in different orders, depending on the embodiment.Any features and/or embodiments described with respect to resampling inthis disclosure may be implemented separately or in any combinationthereof. For example, any features and/or embodiments described inconnection with FIG. 5 may be implemented in any combination with anyfeatures and/or embodiments described in connection with FIG. 4, andvice versa.

Inter-Layer Picture Order in Reference Picture List

In one implementation, three types of inter-layer pictures are possible:motion only inter-layer pictures, sample only inter-layer prediction,and both together. Pictures of all of these types are included into aninter-layer reference picture set. However, pictures with these typesmay not contribute equally to coding efficiency. For example, picturesused for inter-layer sample prediction can be more important thanpicture for inter-layer motion prediction only. Accordingly, it may beadvantageous to have smaller reference indexes for the pictures forinter-layer sample prediction compared to the pictures for inter-layermotion prediction only.

In one embodiment, it is suggested to put the pictures for onlyinter-layer motion prediction at the end of the reference picture setand the initial inter-layer reference picture lists after the picturesfor inter-layer sample prediction. So, the order in the referencepicture list after all temporal reference pictures and in theinter-layer reference picture set can be as follows by dividing picturesinto two sub-sets: pictures for inter-layer sample prediction, picturesfor only inter-layer motion prediction. Similarly to the two partsabove, alternatively, the order in the reference picture list after alltemporal reference pictures and in the inter-layer reference picture setcan be as follows by dividing pictures into three sub-sets: pictures forinter-layer sample and motion prediction, pictures for only inter-layersample prediction, and pictures for only inter-layer motion prediction.Additionally, in each sub-set the ordering can be done in the descendingorder of the inter-layer picture's nuh_layer_id. Alternatively, theorder can follow an explicitly signaled order of the reference layersfor inter-layer prediction, which can be signaled in the VPS orelsewhere.

For the two sub-sets case described above, another type of referencepicture sets can be assigned. For example, a sample inter-layerreference picture set can include pictures used for inter-layer sampleprediction only or both inter-layer sample prediction and inter-layermotion prediction, and a motion inter-layer reference picture set caninclude pictures used for inter-layer motion prediction only.Additionally, the ordering can be applied and motion inter-layerreference picture set can be placed into the initial reference picturelists after sample inter-layer reference picture set. Similarly, for thethree sub-set case, the following new inter-layer reference picture setand the ordering can be applied when placing pictures used forinter-layer prediction into the initial reference picture lists: sampleand motion inter-layer reference picture set, sample only inter-layerreference picture set, and motion only inter-layer reference pictureset. Similarly to the sub-sets, in each new inter-layer referencepicture set the picture ordering can be done in the descending order ofthe inter-layer picture's nuh_layer_id.

Reference Indices Signaling

The techniques can provide optimization in signaling reference indexesat PU level and co-located reference index at slice level. For example,the total number of reference pictures used in reference index signalingcan be adjusted, including only the pictures that can be used for interprediction, such that the reference index signaled in block (e.g., CU,PU, etc.) level can use fewer bits. In addition, the total number ofreference pictures used to define the collocated_ref_idx range can beadjusted to include only the pictures that can be used for TMVPderivation, such that the signaling of collocated_ref_idx can use fewerbits.

In some embodiments, the variables NumOnlySampleRefIdxLX andNumOnlyMotionRefIdxLX with X being equal to 0 and 1 are derived asfollows:

NumOnlySampleRefIdxLX = 0 NumOnlyMotionRefIdxLX = 0 for( i = 0; i <=num_ref_idx_lX_active_minus1; i++ ) {   refLayerId = nuh_layer_id ofRefPicListX[ i ]   if( !SamplePredEnabledFlag[ nuh_layer_id ][refLayerId ] )     NumOnlyMotionRefIdxLX ++   if(!MotionPredEnabledFlag[ nuh_layer_id ][ refLayerId ] )    NumOnlySampleRefIdxLX ++ }

1. PU Reference Signaling

In one embodiment, ref_idx_l0[x0][y0] specifies the list 0 referencepicture index for the current prediction unit. The array indices x0, y0specify the location (x0, y0) of the top-left luma sample of theconsidered prediction block relative to the top-left luma sample of thepicture. ref_idx_l1[x0][y0] has the same semantics as ref_idx_l0, withl0 and list 0 replaced by l1 and list 1, respectively. In certainembodiments, the coding process may be changed from the early versionsof SHVC as follows (changes indicated in bold and italics):

Descriptor prediction_unit( x0, y0, nPbW, nPbH ) { ...  if(inter_pred_idc[ x0 ][ y0 ] != PRED_L1 ) { if(num_ref_idx_l0_active_minus1 − NumOnlyMotionRefIdxL0 > 0 ) ref _(—) idx_(—) l0[ x0 ][ y0 ] ae(v)  mvd_coding( x0, y0, 0 )  mvp _(—) l0 _(—)flag[ x0 ][ y0 ] ae(v)  }  if( inter_pred_idc[ x0 ][ y0 ] != PRED_L0 ) {if( num_ref_idx_l1_active_minus1 − NumOnlyMotionRefIdxL1 > 0 ) ref _(—)idx _(—) l1[ x0 ][ y0 ] ae(v) if( mvd_l1_zero_flag && inter_pred_idc[ x0][ y0 ] = = PRED_BI ) { MvdL1[ x0 ][ y0 ][ 0 ] = 0 MvdL1[ x0 ][ y0 ][ 1] = 0 } else mvd_coding( x0, y0, 1 ) mvp _(—) l1 _(—) flag[ x0 ][ y0 ]ae(v) } ...

ref_idx_lX[x0][y0] is adjusted as follows with X being equal to 0 and 1:

RefIdxNum = ref_idx_lX[x0][y0] for( i = 0; i <= RefIdxNum; i++ ) {  refLayerId = nuh_layer_id of the RefPicListX[ i ]   if(!SamplePredEnabledFlag[ nuh_layer_id ][refLayerId ] )    ref_idx_lX[x0][y0]++  }

2. Collocated Reference Index Signaling

In one embodiment, collocated_ref_idx specifies the reference index ofthe collocated picture used for temporal motion vector prediction.

When slice_type is equal to P or when slice_type is equal to B andcollocated_from_l0 is equal to 1, collocated_ref_idx refers to a picturein list 0, and the value of collocated_ref_idx should be in the range of0 to num_ref_idx_l0 active_minus1-NumOnlySampleRefIdxL0, inclusive.

When slice_type is equal to B and collocated_from_l0 is equal to 0,collocated_ref_idx refers to a picture in list 1, and the value ofcollocated_ref_idx should be in the range of 0 to num_ref_idx_l1active_minus1-NumOnlySampleRefIdxL1, inclusive.

It is a requirement of bitstream conformance that the picture referredto by collocated_ref_idx should be the same for all slices of a codedpicture.

collocated_ref_idx is adjusted as follows:

RefIdxNum = collocated_ref_idx for( i = 0; i <= RefIdxNum; i++ ) {  refLayerId = nuh_layer_id of the RefPicListX[ i ]   if(!MotionPredEnabledFlag[ nuh_layer_id ][ refLayerId ] )  collocated_ref_idx++ }

with X being equal to collocated_from_l0.

TERMINOLOGY

While the above disclosure has described particular embodiments, manyvariations are possible. For example, as mentioned above, the abovetechniques may be applied to 3D video encoding. In some embodiments of3D video, a reference layer (e.g., a base layer) includes videoinformation sufficient to display a first view of a video and theenhancement layer includes additional video information relative to thereference layer such that the reference layer and the enhancement layertogether include video information sufficient to display a second viewof the video. These two views can used to generate a stereoscopic image.As discussed above, motion information from the reference layer can beused to identify additional implicit hypothesis when encoding ordecoding a video unit in the enhancement layer, in accordance withaspects of the disclosure. This can provide greater coding efficiencyfor a 3D video bitstream.

It is to be recognized that depending on the example, certain acts orevents of any of the techniques described herein can be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,not all described acts or events are necessary for the practice of thetechniques). Moreover, in certain examples, acts or events may beperformed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors, rather than sequentially.

Information and signals disclosed herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative logical blocks, modules, circuits, andalgorithm steps described in connection with the embodiments disclosedherein may be implemented as electronic hardware, computer software, orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentinvention.

The techniques described herein may be implemented in hardware,software, firmware, or any combination thereof. Such techniques may beimplemented in any of a variety of devices such as general purposescomputers, wireless communication device handsets, or integrated circuitdevices having multiple uses including application in wirelesscommunication device handsets and other devices. Any features describedas modules or components may be implemented together in an integratedlogic device or separately as discrete but interoperable logic devices.If implemented in software, the techniques may be realized at least inpart by a computer-readable data storage medium comprising program codeincluding instructions that, when executed, performs one or more of themethods described above. The computer-readable data storage medium mayform part of a computer program product, which may include packagingmaterials. The computer-readable medium may comprise memory or datastorage media, such as random access memory (RAM) such as synchronousdynamic random access memory (SDRAM), read-only memory (ROM),non-volatile random access memory (NVRAM), electrically erasableprogrammable read-only memory (EEPROM), FLASH memory, magnetic oroptical data storage media, and the like. The techniques additionally,or alternatively, may be realized at least in part by acomputer-readable communication medium that carries or communicatesprogram code in the form of instructions or data structures and that canbe accessed, read, and/or executed by a computer, such as propagatedsignals or waves.

The program code may be executed by a processor, which may include oneor more processors, such as one or more digital signal processors(DSPs), general purpose microprocessors, an application specificintegrated circuits (ASICs), field programmable logic arrays (FPGAs), orother equivalent integrated or discrete logic circuitry. Such aprocessor may be configured to perform any of the techniques describedin this disclosure. A general purpose processor may be a microprocessor;but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration. Accordingly, the term “processor,” as used herein mayrefer to any of the foregoing structure, any combination of theforegoing structure, or any other structure or apparatus suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated software modules or hardware modules configured for encodingand decoding, or incorporated in a combined video encoder-decoder(CODEC).

The coding techniques discussed herein may be embodiment in an examplevideo encoding and decoding system. A system includes a source devicethat provides encoded video data to be decoded at a later time by adestination device. In particular, the source device provides the videodata to destination device via a computer-readable medium. The sourcedevice and the destination device may comprise any of a wide range ofdevices, including desktop computers, notebook (i.e., laptop) computers,tablet computers, set-top boxes, telephone handsets such as so-called“smart” phones, so-called “smart” pads, televisions, cameras, displaydevices, digital media players, video gaming consoles, video streamingdevice, or the like. In some cases, the source device and thedestination device may be equipped for wireless communication.

The destination device may receive the encoded video data to be decodedvia the computer-readable medium. The computer-readable medium maycomprise any type of medium or device capable of moving the encodedvideo data from source device to destination device. In one example,computer-readable medium may comprise a communication medium to enablesource device 12 to transmit encoded video data directly to destinationdevice in real-time. The encoded video data may be modulated accordingto a communication standard, such as a wireless communication protocol,and transmitted to destination device. The communication medium maycomprise any wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network such as theInternet. The communication medium may include routers, switches, basestations, or any other equipment that may be useful to facilitatecommunication from source device to destination device.

In some examples, encoded data may be output from output interface to astorage device. Similarly, encoded data may be accessed from the storagedevice by input interface. The storage device may include any of avariety of distributed or locally accessed data storage media such as ahard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile ornon-volatile memory, or any other suitable digital storage media forstoring encoded video data. In a further example, the storage device maycorrespond to a file server or another intermediate storage device thatmay store the encoded video generated by source device. Destinationdevice may access stored video data from the storage device viastreaming or download. The file server may be any type of server capableof storing encoded video data and transmitting that encoded video datato the destination device. Example file servers include a web server(e.g., for a website), an FTP server, network attached storage (NAS)devices, or a local disk drive. Destination device may access theencoded video data through any standard data connection, including anInternet connection. This may include a wireless channel (e.g., a Wi-Ficonnection), a wired connection (e.g., DSL, cable modem, etc.), or acombination of both that is suitable for accessing encoded video datastored on a file server. The transmission of encoded video data from thestorage device may be a streaming transmission, a download transmission,or a combination thereof.

The techniques of this disclosure are not necessarily limited towireless applications or settings. The techniques may be applied tovideo coding in support of any of a variety of multimedia applications,such as over-the-air television broadcasts, cable televisiontransmissions, satellite television transmissions, Internet streamingvideo transmissions, such as dynamic adaptive streaming over HTTP(DASH), digital video that is encoded onto a data storage medium,decoding of digital video stored on a data storage medium, or otherapplications. In some examples, system may be configured to supportone-way or two-way video transmission to support applications such asvideo streaming, video playback, video broadcasting, and/or videotelephony.

In one example the source device includes a video source, a videoencoder, and a output interface. The destination device may includeinclude an input interface, a video decoder, and a display device. Thevideo encoder of source device may be configured to apply the techniquesdisclosed herein. In other examples, a source device and a destinationdevice may include other components or arrangements. For example, thesource device may receive video data from an external video source, suchas an external camera. Likewise, the destination device may interfacewith an external display device, rather than including an integrateddisplay device.

The example system above merely one example. Techniques for processingvideo data in parallel may be performed by any digital video encodingand/or decoding device. Although generally the techniques of thisdisclosure are performed by a video encoding device, the techniques mayalso be performed by a video encoder/decoder, typically referred to as a“CODEC.” Moreover, the techniques of this disclosure may also beperformed by a video preprocessor. Source device and destination deviceare merely examples of such coding devices in which source devicegenerates coded video data for transmission to destination device. Insome examples, the source and destination devices may operate in asubstantially symmetrical manner such that each of the devices includesvideo encoding and decoding components. Hence, example systems maysupport one-way or two-way video transmission between video devices,e.g., for video streaming, video playback, video broadcasting, or videotelephony.

The video source may include a video capture device, such as a videocamera, a video archive containing previously captured video, and/or avideo feed interface to receive video from a video content provider. Asa further alternative, the video source may generate computergraphics-based data as the source video, or a combination of live video,archived video, and computer-generated video. In some cases, if videosource is a video camera, source device and destination device may formso-called camera phones or video phones. As mentioned above, however,the techniques described in this disclosure may be applicable to videocoding in general, and may be applied to wireless and/or wiredapplications. In each case, the captured, pre-captured, orcomputer-generated video may be encoded by the video encoder. Theencoded video information may then be output by output interface ontothe computer-readable medium.

As noted the computer-readable medium may include transient media, suchas a wireless broadcast or wired network transmission, or storage media(that is, non-transitory storage media), such as a hard disk, flashdrive, compact disc, digital video disc, Blu-ray disc, or othercomputer-readable media. In some examples, a network server (not shown)may receive encoded video data from the source device and provide theencoded video data to the destination device, e.g., via networktransmission. Similarly, a computing device of a medium productionfacility, such as a disc stamping facility, may receive encoded videodata from the source device and produce a disc containing the encodedvideo data. Therefore, the computer-readable medium may be understood toinclude one or more computer-readable media of various forms, in variousexamples.

The input interface of the destination device receives information fromthe computer-readable medium. The information of the computer-readablemedium may include syntax information defined by the video encoder,which is also used by the video decoder, that includes syntax elementsthat describe characteristics and/or processing of blocks and othercoded units, e.g., group of pictures (GOP). A display device displaysthe decoded video data to a user, and may comprise any of a variety ofdisplay devices such as a cathode ray tube (CRT), a liquid crystaldisplay (LCD), a plasma display, an organic light emitting diode (OLED)display, or another type of display device. Various embodiments of theinvention have been described. These and other embodiments are withinthe scope of the following claims.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

What is claimed is:
 1. An apparatus configured to code videoinformation, the apparatus comprising: a memory configured to storevideo information; and computing hardware operationally coupled to thememory and configured to: identify a current picture to be predictedusing at least one type of inter layer prediction (ILP), the type of ILPcomprising inter layer motion prediction (ILMP), or inter layer sampleprediction (ILSP), or both; when the current picture is to be predictedusing at least ILMP: process a collocated reference index valueassociated with the current picture, wherein the collocated referenceindex value indicates a first reference picture that is used inpredicting the current picture using ILP; determine whether the firstreference picture indicated by the collocated reference index value isenabled for ILMP; and when the current picture is to be predicted usingat least ILSP: process a reference index value associated with a blockin the current picture, wherein the reference index value indicates asecond reference picture that is used in predicting the block in thecurrent picture using ILP; and determine whether the second referencepicture indicated by the reference index value is enabled for ILSP. 2.The apparatus of claim 1, wherein the computing hardware is configuredto determine whether the first reference picture is enabled for ILMP bydetermining a value of the motion prediction enabled flag for the firstreference picture.
 3. The apparatus of claim 2, wherein the computinghardware is further configured to determine that the first referencepicture is enabled for ILMP when the motion prediction enabled flagvalue is equal to
 1. 4. The apparatus of claim 2, wherein the computinghardware is further configured to determine that the first referencepicture is not enabled for ILMP when the motion prediction enabled flagvalue is equal to
 0. 5. The apparatus of claim 1, wherein the computinghardware is configured to determine whether the second reference pictureis enabled for ILSP by determining a value of the sample predictionenabled flag for the second reference picture.
 6. The apparatus of claim5, wherein the computing hardware is further configured to determinethat the second reference picture is enabled for ILSP when the sampleprediction enabled flag value is equal to
 1. 7. The apparatus of claim5, wherein the computing hardware is further configured to determinethat the second reference picture is not enabled for ILSP when thesample prediction enabled flag value is equal to
 0. 8. The apparatus ofclaim 1, wherein the computing hardware is further configured to signalthe collocated reference index value in a bitstream when the firstreference picture is enabled for ILMP, or signal the reference indexvalue in the bitstream when the second reference picture is enabled forILSP, or both.
 9. The apparatus of claim 1, wherein the computinghardware is further configured to receive the collocated reference indexor the reference index in a bitstream.
 10. The apparatus of claim 1,wherein the computing hardware is further configured to encode thecollocated reference index value in a bitstream when the first referencepicture is enabled for ILMP, or encode the reference index value in thebitstream when the second reference picture is enabled for ILSP, orboth.
 11. The apparatus of claim 1, wherein the computing hardware isfurther configured to decode the collocated reference index or thereference index in a bitstream.
 12. The apparatus of claim 1, whereinthe apparatus is selected from a group consisting of one or more of: adesktop computer, a notebook computer, a laptop computer, a tabletcomputer, a set-top box, a telephone handset, a smart phone, a smartpad, a television, a camera, a display device, a digital media player, avideo gaming console, and a video streaming device.
 13. A method ofcoding video information, the method comprising: identifying a currentpicture to be predicted using at least one type of inter layerprediction (ILP), the type of ILP comprising inter layer motionprediction (ILMP), or inter layer sample prediction (ILSP), or both;when the current picture is to be predicted using at least ILMP:processing a collocated reference index value associated with thecurrent picture, wherein the collocated reference index value indicatesa first reference picture that is used in predicting the current pictureusing ILP; and determining whether the first reference picture indicatedby the collocated reference index value is enabled for ILMP; and whenthe current picture is to be predicted using at least ILSP: processing areference index value associated with a block in the current picture,wherein the reference index value indicates a second reference picturethat is used in predicting the block in the current picture using ILP;and determining whether the second reference picture indicated by thereference index value is enabled for ILSP.
 14. The method of claim 13,wherein said determining whether the first reference picture is enabledfor ILMP comprises determining a value of the motion prediction enabledflag for the first reference picture.
 15. The method of claim 14,further comprising determining that the first reference picture isenabled for ILMP when the motion prediction enabled flag value is equalto
 1. 16. The method of claim 14, further comprising determining thatthe first reference picture is not enabled for ILMP when the motionprediction enabled flag value is equal to
 0. 17. The method of claim 13,wherein said determining whether the second reference picture is enabledfor ILSP comprises determining a value of the sample prediction enabledflag for the second reference picture.
 18. The method of claim 17,further comprising determining that the second reference picture isenabled for ILSP when the sample prediction enabled flag value is equalto
 1. 19. The method of claim 17, further comprising determining thatthe second reference picture is not enabled for ILSP when the sampleprediction enabled flag value is equal to
 0. 20. The method of claim 13,further comprising signaling the collocated reference index value in abitstream when the first reference picture is enabled for ILMP, orsignaling the reference index value in the bitstream when the secondreference picture is enabled for ILSP, or both.
 21. The method of claim13, further comprising receiving the collocated reference index or thereference index in a bitstream.
 22. The method of claim 13, furthercomprising encoding the collocated reference index value in a bitstreamwhen the first reference picture is enabled for ILMP, or encoding thereference index value in the bitstream when the second reference pictureis enabled for ILSP, or both.
 23. The method of claim 13, furthercomprising decoding the collocated reference index or the referenceindex in a bitstream.
 24. A non-transitory computer readable mediumcomprising instructions that when executed on a processor comprisingcomputer hardware cause the processor to: identify a current picture tobe predicted using at least one type of inter layer prediction (ILP),the type of ILP comprising inter layer motion prediction (ILMP), orinter layer sample prediction (ILSP), or both; when the current pictureis to be predicted using at least ILMP: process a collocated referenceindex value associated with the current picture, wherein the collocatedreference index value indicates a first reference picture that is usedin predicting the current picture using ILP; and determine whether thefirst reference picture indicated by the collocated reference indexvalue is enabled for ILMP; and when the current picture is to bepredicted using at least ILSP: process a reference index valueassociated with a block in the current picture, wherein the referenceindex value indicates a second reference picture that is used inpredicting the block in the current picture using ILP; and determinewhether the second reference picture indicated by the reference indexvalue is enabled for ILSP.
 25. The computer readable medium of claim 24,further comprising instructions that cause the processor to determinewhether the first reference picture is enabled for ILMP by determining avalue of the motion prediction enabled flag for the first referencepicture.
 26. The computer readable medium of claim 24, furthercomprising instructions that cause the processor to determine whetherthe second reference picture is enabled for ILSP by determining a valueof the sample prediction enabled flag for the second reference picture.27. An apparatus configured to code video information, the apparatuscomprising: means for storing video information; means for identifying acurrent picture to be predicted using at least one type of inter layerprediction (ILP), the type of ILP comprising inter layer motionprediction (ILMP), or inter layer sample prediction (ILSP), or both;means for, when the current picture is to be predicted using at leastILMP, processing a collocated reference index value associated with thecurrent picture, wherein the collocated reference index value indicatesa first reference picture that is used in predicting the current pictureusing ILP, the means for processing the collocated reference index valuefurther configured to determine whether the first reference pictureindicated by the collocated reference index value is enabled for ILMP;and means for, when the current picture is to be predicted using atleast ILSP, processing a reference index value associated with a blockin the current picture, wherein the reference index value indicates asecond reference picture that is used in predicting the block in thecurrent picture using ILP, the means for processing the reference indexvalue further configured to determine whether the second referencepicture indicated by the reference index value is enabled for ILSP. 28.The apparatus of claim 27, wherein the means for determining whether thefirst reference picture is enabled for ILMP is configured to determinewhether the first reference picture is enabled for ILMP by determining avalue of the motion prediction enabled flag for the first referencepicture.
 29. The apparatus of claim 27, wherein the means fordetermining whether the second reference picture is enabled for ILSP isconfigured to determine whether the second reference picture is enabledfor ILSP by determining a value of the sample prediction enabled flagfor the second reference picture.